The underlined verbs in the sentences are correct. Here is an explanation for each sentence:
1. Water boils at 100 degrees Celsius.
- The verb "boils" is correctly used in the present simple tense to describe a general truth or fact.
2. How often are you going to the cinema?
- The verb "are going" is correctly used in the present continuous tense to describe a recurring action or habit.
3. Ben tries to find a job, but he hasn't had any luck yet.
- The verb "tries" is correctly used in the present simple tense to describe an action that is happening now or regularly.
4. Martina is phoning her mother every day.
- The verb "is phoning" is correctly used in the present continuous tense to describe an action that is happening at the moment of speaking.
5. The moon goes round the earth in about 27 days.
- The verb "goes" is correctly used in the present simple tense to describe a natural process or a fact.
In conclusion, all the underlined verbs in the sentences are appropriate and do not need correction.
