Select the most appropriate synonym of the underlined word in the given sentence.
Can I please request you all to stand up?

The correct answer is plead.

Explanation:

In the given sentence, "request" means to politely or formally ask for something.

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

1. claim: To state or assert that something is the case, typically without providing proof.

2. petition: A formal written request, typically one signed by many people, appealing to authority in respect of a particular cause.

3. plead: To make an emotional or earnest appeal, or to ask earnestly/beg for something. In context, it serves as the closest synonym for "request".

4. require: To need something or make something necessary; to demand.

Therefore, among the given options, plead is the most appropriate synonym for the word request.