**Step 1: Identify the relevant industry**
Bouygues is a diversified industrial group with major operations in construction, property development, and telecommunications (via Bouygues Telecom). It does not fit into the specific S&P methodologies provided for Regulated Utilities, Oil & Gas Exploration and Production, Unregulated Power and Gas, or Transportation Infrastructure. Therefore, we will apply the general corporate baseline formulas provided in the subsequent steps.

**Step 2: Estimate the 2021 Adjusted_EBITDA**
Formula: Adjusted_EBITDA = EBITDA (reported or reconstructed) + adjustment_leases + nonrecurring_losses - nonrecurring_gains ± other_normalization_adjustments
- Reported Profit Loss From Operating Activities (EBIT) for 2021: €1,733,000,000
- Depreciation And Amortisation Expense: €2,065,000,000
- Depreciation Right-of-use Assets: €353,000,000
- EBITDA = EBIT + D&A = 1,733,000,000 + 2,065,000,000 + 353,000,000 = €4,151,000,000
- Adjustment for leases: Under S&P corporate methodology, operating lease expenses recorded within EBIT are adjusted by adding back the lease expense and subtracting the depreciation of RoU assets to avoid double counting. 
  Lease interest expense: €52,000,000
  Lease depreciation expense: €353,000,000
  Lease adjustment = Lease interest - Lease depreciation = 52,000,000 - 353,000,000 = -€301,000,000
- Non-recurring items: Other Operating Income Non-Recurring (€115,000,000) - Other Operating Expense Non-Recurring (€75,000,000) = Net non-recurring gain of €40,000,000. We subtract this to normalize EBITDA.
- Adjusted_EBITDA 2021 = 4,151,000,000 - 301,000,000 - 40,000,000 = €3,810,000,000

**Step 3: Estimate the 2021 FFO**
Formula: FFO = Adjusted_EBITDA - cash_interest - cash_taxes
- Cash interest: Interest Expense on Lease Liabilities (€52,000,000) + Interest Paid Classified As Financing Activities (€207,000,000) = €259,000,000
- Cash taxes: Income Taxes Paid Classified As Operating Activities (€397,000,000)
- FFO 2021 = 3,810,000,000 - 259,000,000 - 397,000,000 = €3,154,000,000

**Step 4: Estimate the 2021 Adjusted_Debt**
Formula: Adjusted_Debt = (reported_debt + leases + other_debt_like_items) - eligible_cash
- Reported debt: Long-term borrowings (€5,805,000,000) + Current borrowings (€1,324,000,000) + Short-term borrowings from banks (€351,000,000) = €7,480,000,000
- Leases: Noncurrent lease liabilities (€1,473,000,000) + Current lease liabilities (€362,000,000) = €1,835,000,000
- Eligible cash: Cash And Cash Equivalents (€6,501,000,000)
- Adjusted_Debt 2021 = 7,480,000,000 + 1,835,000,000 - 6,501,000,000 = €2,814,000,000

**Step 5: Calculate 2021 Adjusted_Debt / Adjusted_EBITDA**
- Ratio 2021 = 2,814,000,000 / 3,810,000,000 = 0.74x

**Step 6: Calculate 2021 FFO / Adjusted_Debt**
- Ratio 2021 = 3,154,000,000 / 2,814,000,000 = 112.1% (or 1.121)

**Step 7: Estimate the 2022 Adjusted_EBITDA**
- Reported Profit Loss From Operating Activities (EBIT) for 2022: €1,872,000,000
- Depreciation And Amortisation Expense: €2,228,000,000
- Depreciation Right-of-use Assets: €446,000,000
- EBITDA = 1,872,000,000 + 2,228,000,000 + 446,000,000 = €4,546,000,000
- Adjustment for leases: Lease interest expense (€62,000,000) - Lease depreciation expense (€446,000,000) = -€384,000,000
- Non-recurring items: Other Operating Income Non-Recurring (€93,000,000) - Other Operating Expense Non-Recurring (€183,000,000) = Net non-recurring loss of €90,000,000. We add this back to normalize.
- Adjusted_EBITDA 2022 = 4,546,000,000 - 384,000,000 + 90,000,000 = €4,252,000,000

**Step 8: Estimate the 2022 FFO**
- Cash interest: Interest Expense on Lease Liabilities (€62,000,000) + Interest Paid Classified As Financing Activities (€260,000,000) = €322,000,000
- Cash taxes: Income Taxes Paid Classified As Operating Activities (€518,000,000)
- FFO 2022 = 4,252,000,000 - 322,000,000 - 518,000,000 = €3,412,000,000

**Step 9: Estimate the 2022 Adjusted_Debt**
- Reported debt: Long-term borrowings (€11,586,000,000) + Current borrowings (€1,361,000,000) + Short-term borrowings from banks (€418,000,000) = €13,365,000,000
- Leases: Noncurrent lease liabilities (€2,107,000,000) + Current lease liabilities (€498,000,000) = €2,605,000,000
- Eligible cash: Cash And Cash Equivalents (€5,736,000,000)
- Adjusted_Debt 2022 = 13,365,000,000 + 2,605,000,000 - 5,736,000,000 = €10,234,000,000

**Step 10: Calculate 2022 Adjusted_Debt / Adjusted_EBITDA**
- Ratio 2022 = 10,234,000,000 / 4,252,000,000 = 2.41x

**Step 11: Calculate 2022 FFO / Adjusted_Debt**
- Ratio 2022 = 3,412,000,000 / 10,234,000,000 = 33.3% (or 0.333)

**Step 12: Classify the year-on-year credit trend**
- Signal 1 (Leverage): Change in Adjusted_Debt / Adjusted_EBITDA = 2.41x - 0.74x = +1.67x. 
  Threshold: ≥ +0.2x indicates **Deteriorating**.
- Signal 2 (Cash-flow coverage): Change in FFO / Adjusted_Debt = 0.333 - 1.121 = -0.788. 
  Threshold: ≤ -0.03 indicates **Deteriorating**.
- Both signals strongly agree on a significant deterioration in credit metrics primarily driven by a massive increase in adjusted debt (mostly from long-term borrowings surging from €5.8B to €11.6B, reflecting the acquisition of Equans).

<answer>Deteriorating</answer>