Only those who ave completed eighteen years are . . . . . . . . to apply for this post.

The correct answer is: E. eligible

The word “eligible” means “qualified or fit to be chosen or elected.” In this case, the sentence is saying that only people who have completed eighteen years are qualified to apply for the post.

The other options are not correct because:

• “Elected” means “chosen by a vote.” This is not what the sentence is saying.
• “Legible” means “able to be read.” This is not what the sentence is saying.
• “Selected” means “chosen from a group.” This is not what the sentence is saying.
• “Forced” means “made to do something against one’s will.” This is not what the sentence is saying.