In Nigeria, the idea of taking a vacation cannot be said to have -72-. This is not -73- that Nigerians are not -74- of travelling. The people travel so -75-...

The best option that completes the gap is "ensures." The sentence talks about a builder who is about to erect a building, and the word "then" indicates a sequence of events. The verb that best fits in the sentence should indicate an action that the builder takes to make sure that the bricks are of the recommended quality. The word "ensures" means making something certain to happen or guaranteeing it. Therefore, the best option that completes the gap is "ensures" because it implies that the builder takes the necessary steps to guarantee that the bricks are of the recommended quality. Option B, "assures," is not the best option because it means to tell someone that something is definitely true or is definitely going to happen, and it does not fit in the context of the sentence. Option C, "presumes," means to suppose something is true without evidence, which is not the right word to use in the sentence. Option D, "insures," means to protect something against loss or damage, which is not relevant to the sentence. Option E, "assumes," means to take for granted without verifying, which is not suitable in the context of the sentence. In conclusion, the correct sentence should be "He ensures that the bricks are of the recommended quality by checking them."