The correct answer is be study.

Step-by-Step Explanation:

1. Analyze the Sentence Structure:
The given sentence is "I will be study around 7 o’clock."

2. Identify the Grammatical Error:
The phrase uses the future continuous tense structure, which follows the rule:

$\text{Subject}+\text{will be}+\text{verb (-ing form)}$

3. Correct Sentence:
"I will be studying around 7 o’clock."

Therefore, the part of the sentence containing the error is "be study".