Select the most appropriate option to fill in the blank.

We should ______ his outfit as he has put on weight.

alter

The most appropriate option to fill in the blank is alter.

The word "alter" means to change or modify something. This is the most appropriate word because it accurately describes how the outfit should be changed to fit the person's new body size.

The other options are not as appropriate.

• Altar is a raised platform in a place of worship. It does not make sense in the context of the sentence, because the outfit is not being raised to a platform.
• Ultra means extremely or very. It does not make sense in the context of the sentence, because the outfit does not need to be changed extremely or very much.
• Utter means to say something completely or fully. It does not make sense in the context of the sentence, because the outfit is not being said completely or fully.