Terna is a regulated electricity transmission utility with stable operating cash flows and strong asset backing, so it can support significant leverage. However, hybrid bonds should be used as a complement to senior debt and equity, not as the dominant funding source.

Key considerations:

- The company already issued a large perpetual hybrid bond in 2022: €989 million, recorded in equity instruments.
- Total equity rose to €6.17 billion, with the hybrid representing roughly 16% of total equity and around 19% of equity attributable to owners excluding non-controlling interests.
- Debt remains substantial: long-term borrowings of €8.42 billion plus short-term/current borrowings of about €2.35 billion, so the company is still primarily debt-funded.
- Operating performance is strong: 2022 operating profit was €1.33 billion, profit was €858 million, and operating cash flow was €2.32 billion.
- Interest-rate conditions worsened sharply in 2022, with euro swap rates rising from near-zero/negative levels to around 1.7%–1.9%, and investment-grade credit spreads also higher. This makes excessive reliance on hybrid issuance less attractive.
- Hybrid bonds are useful because rating agencies often grant partial equity credit and because they help support credit metrics during a heavy investment cycle. But they are typically more expensive than senior debt and can increase refinancing/coupon-reset risk.
- Given Terna’s regulated, infrastructure-like profile, a moderate hybrid allocation is appropriate: enough to strengthen capital structure flexibility, but not enough to materially burden financing costs.

Therefore, among the available choices, the best fit is a limited-to-moderate reliance on hybrid bonds.

<answer>25%</answer>