Let’s break down the reasoning step-by-step.

**1. Understanding the S&P cap**  
S&P limits the equity credit from hybrid bonds to 15% of total adjusted capital (debt + equity).  
For Terna as of 2023-01-01:  
- Equity = €6,169.1M  
- Noncurrent financial liabilities + current financial liabilities + long-term borrowings + short-term borrowings + current portion of long-term borrowings = debt  
- Debt = €247.2M + €44.9M + €8,416.7M + €444.1M + €1,909.3M = ~€11,062.2M  
- Total adjusted capital = €6,169.1M + €11,062.2M = €17,231.3M  
- 15% cap = €2,584.7M

**2. Current hybrid usage**  
From the data:  
- Perpetual hybrid bonds (equity instruments) issued in FY2022: €989M.  
This is already included within equity (Capital Instruments Bonds Hybrid Perpetual line).  
Existing hybrids = €989M, which is about 5.7% of total adjusted capital, well below the 15% cap.

**3. Why might they issue more?**  
- Interest rates rose sharply in 2022 (swap curves went from negative to ~2%), making fixed-rate debt more expensive.  
- Hybrids get partial equity treatment by rating agencies, helping maintain credit metrics while financing CapEx.  
- Terna’s CapEx is high (€1.49B in 2022), so they need efficient capital structures.

**4. How much more can they issue?**  
Remaining room under cap = €2,584.7M – €989M = ~€1,595.7M.  
Thus they could more than double the current hybrid amount before hitting the cap.

**5. Extent of utilization**  
The question is “to what extent should they utilize hybrids relative to the cap?”  
Given their infrastructure-heavy business, stable cash flows, and the need to fund significant investment while keeping leverage manageable, fully utilizing the cap seems reasonable. Issuing up to the cap (100%) would maximize equity credit and support credit ratings without a disproportionate cost, especially as hybrid coupons became more attractive in the rising-rate environment.

Therefore, **100%** is the logical choice.

<answer>100%</answer>