The correct option is A At this time tomorrow, I will leave.
Tense is used to provide more information about an action ( its time, completeness, etc.). Option A)At this time tomorrow, I will leave. is correct as the given sentence must be changed into the simple future tense and will+present participle is the correct structure for the simple future tense. The other options are wrong as no other tense can be used here. The correct answer is A)At this time tomorrow, I will leave.