Which of the following is a legal constraint on government borrowing?

The correct choice is based on the principle that a government must maintain a sustainable level of debt in relation to its financial health. Legal constraints on government borrowing typically include measures designed to ensure that the amount of debt does not exceed certain thresholds, such as total budget limits or specific ratios related to revenue. This is an essential aspect of sound fiscal management, as it helps prevent excessive borrowing that could jeopardize the government's ability to meet its financial obligations and maintain fiscal stability.

In many jurisdictions, laws or regulations may specify the maximum amount of debt that can be incurred relative to the total budget or revenue levels. This helps governments avoid situations where they are unable to service their debt, which can lead to adverse consequences like default or financial crises.

The other choices do not accurately reflect common legal constraints. For instance, debt exceeding revenue or having unrestricted debt amounts would jeopardize fiscal responsibility, while borrowing strictly for current operational expenses may not account for necessary investments in infrastructure or long-term projects that could enhance future revenues. These aspects underscore the importance of prudent debt management and borrowing practices within the legal framework guiding government finances.