Douglas tried to come to the surface of the pool three times.

Explanation:
1. The question states that Douglas tried to come to the surface of the pool multiple times. We need to determine the exact number of attempts.
2. The options provided are:
a) Twice
b) Once
c) Five times
d) Thrice
3. The correct answer is option d) Thrice, which means Douglas tried to come to the surface of the pool three times.
4. Let's break down the given options to understand why the correct answer is "Thrice":
a) Twice: If Douglas tried to come to the surface of the pool only twice, it would be incorrect because the question clearly mentions that he tried multiple times.
b) Once: If Douglas tried to come to the surface of the pool only once, it would also be incorrect as the question states that he tried multiple times.
c) Five times: If Douglas tried to come to the surface of the pool five times, it would be incorrect because the question does not mention the number of attempts as five.
d) Thrice: This is the correct answer as it indicates that Douglas tried to come to the surface of the pool three times, which aligns with the information given in the question.
5. Therefore, the correct answer is option d) Thrice, as it accurately represents the number of attempts made by Douglas to reach the surface of the pool.