How much time does a terrier have to reach the quarry in an open tunnel?

The correct choice is based on the established standard for performance in terrier events. The designated time for a terrier to reach the quarry in an open tunnel is 30 seconds. This timeframe is meant to ensure that handlers and their dogs are operating within a set limit that balances the dog's natural instinct and speed while also allowing for the handler's guidance and support during the performance.

The time allowed is specifically structured to provide a sufficient challenge that tests both the dog's agility and the handler's training techniques, while also ensuring safety and fairness in competitions where multiple participants may be involved. This standardization of time helps maintain consistency across events and allows judges to fairly evaluate the performances based on how well each team meets the expectations within the allotted time.