Question: Part of the house is leased, he signed a 1-year lease for $6000 on April 1. Payment will be done in 2 opportunities, every 6 months. The first 6 months will be paid on September 30, and the second March 31.

Is it correct to do:
d: Rental Expense 3000
c: Cash 3000

For both September and March dates?

Bump: please answer please

This question is posted in accounting but it could be a legal question too. Having been a landlord I would have to say that this is not how leases normally work. You sign on April 1 you pay on April 1. Leases do not let you live in a play for 6 months rent free, you pay in advance.

This makes no more sense than the other one you posted, clearly homework.
Your choices here are d and c. What happened to a and b?
What's the fiscal year and method?

You should not treat accounting entries as some sort of cell shorthand, as raw data your entries are correct