Let’s break this down using the provided framework.

**Entity A – Terna S.p.A.**  
- **Sector:** Regulated electricity transmission (pure infrastructure, highly visible cash flows).  
- **Credit profile:** Investment grade (BBB area typical for Terna).  
- **Hybrids already issued:** Yes, clearly—there is a 989 M EUR “Equity Instruments Perpetual Hybrid Bonds” line, meaning they already use this instrument.  
- **Refinancing need:** No explicit near-term call date visible, but the existence of hybrids means a potential call/refinancing risk in the next 18 months is plausible.  
- **Leverage improvement:** Large capex program (1.49 B EUR in 2022 purchases of PP&E), high debt; additional hybrid would improve FFO/debt and rating headroom.  
- **Cost consideration:** Average cost of debt appears moderate (~1.4 % interest based on finance costs and gross debt), so marginal cost of hybrid is not a strong negative.  
- **Overall fit:** **Strongly suitable**.

**Entity B – A2A Energia (A2A S.p.A.)**  
- **Sector:** Multi-utility, partially regulated, some merchant exposure (generation, energy sales). Less pure infrastructure than Terna.  
- **Credit profile:** Likely investment grade, but more cyclical and industrial exposure.  
- **Hybrids:** No indication of existing hybrids, no clear “must-refinance” trigger.  
- **Rationale for hybrid:** Could support M&A, capex, or temporary balance-sheet strength, but more opportunistic than structural.  
- **Cash flow visibility:** Good but not as predictable as pure TSO.  
- **Overall fit:** Fits **Marginally suitable** — would be an opportunistic issuer rather than one with strong structural rationale.

**Entity C – Redeia Corporación (Red Eléctrica)**  
- **Sector:** Electricity TSO in Spain, plus telecom/infra via subsidiaries. Highly regulated, predictable cash flows.  
- **Credit profile:** Solid investment grade, slightly weaker leverage due to large investment in Hispasat, but still infrastructure-like.  
- **Hybrids/refinancing:** No existing hybrids explicitly shown, but significant financing activity (large bond issuance/redemptions); possible refinancing rationale.  
- **Leverage metrics:** Large capex and financial investment program; hybrid would clearly improve adjusted leverage.  
- **Cost of hybrid:** Average cost of debt around 2 %, hybrid marginal cost is acceptable.  
- **Overall fit:** **Strongly suitable**, but secondary to Terna because Terna already has outstanding hybrids (likely call approaching) and slightly higher immediate refinancing pressure.

**Ordering:**  
1. **A** – strongest case, existing hybrid maturity/refinancing angle, top-tier regulated infrastructure, clear rating benefit.  
2. **C** – equally strong sector, slight edge over B because of pure infrastructure/utility profile, clear leverage improvement need.  
3. **B** – more industrial/mixed, no existing hybrid, fit is opportunistic rather than structural.

<answer>A,C,B</answer>