The correct answer is B. Eager for the game to start again, he watched the half-time clock.
Explanation:
The hyphen (-) is a common punctuation mark, mainly used to join two or more words and combining the meaning of them. Because of this hyphen is used in the case of two or more adjectives that are placed before the noun they describe; in the case of compound words such as brother-in-law; in the case of fractions of compound numbers or in some cases to clarify when two or more words need to be understood as one in case this changes the meaning. Considering this, in the case of the sentence "Eager for the game to start again, he watched the half time clock" the hyphen should be placed to join the words "half" and "time", considering the word "half-time" acts as a compound adjective to describe clock. Therefore, the sentence that shows the correct use of the hyphen is B. "Eager for the game to start again, he watched the half-time clock".