Select the most appropriate option to fill in the blank.

I ______ very busy lately.

have been

The correct option to fill in the blank is have been.

The sentence is about the speaker's current state of being busy. The speaker is using the past perfect tense "have been" to indicate that they have been busy for a period of time that is still ongoing. The other options are not as appropriate.

• Would be is the conditional tense, which is used to talk about hypothetical situations. It does not make sense to use the conditional tense in this context because the speaker is not talking about a hypothetical situation, they are talking about their current state of being busy.
• Will be is the future tense, which is used to talk about things that will happen in the future. It does not make sense to use the future tense in this context because the speaker is talking about their current state of being busy, which is already happening.
• Should be is the modal verb "should", which is used to express obligation or necessity. It does not make sense to use the modal verb "should" in this context because the speaker is not talking about something that they are obliged to do, they are simply stating that they are busy.