Select the most appropriate phrase for the underlined segment in the given sentence.

My mother said, “You must pay attention to your studies.”

Concentrate on

The most appropriate phrase for the underlined segment in the given sentence is (1) Concentrate on.

The other options do not fit the context of the sentence.

• To concentrate on something means to focus your attention on it.
• To back up something means to support or defend it.
• To act up to something means to live up to or fulfill it.
• To ask for something means to request it.

In the given sentence, the mother is telling her child to focus their attention on their studies. The phrase "pay attention" is a synonym for "concentrate" and is the most appropriate way to express this meaning.