Select the most appropriate synonym of the underlined word in the given sentence.
Mr. Satterthwaite was shrewd enough to penetrate her meaning.

The correct option is Smart.

Explanation:
In the given sentence, "Mr. Satterthwaite was shrewd enough to penetrate her meaning," the word shrewd means having or showing sharp powers of judgment, keen insight, or intelligence.

Let's look at the meanings of the given options:

1. Aged: Having lived for a long time; old.

2. Funny: Causing laughter or amusement; humorous.

3. Innocent: Not guilty of a crime or offence; harmless or naive.

4. Smart: Having or showing a quick-witted intelligence; clever or astute.

Since shrewd and smart both describe someone who is sharp, perceptive, and intelligent, Smart is the most appropriate synonym.