Answer: February 12
Explanation:
Part of the Texas Real Estate Commission(TREC) Residential Agreement calls for the Seller to send a Seller's Disclosure to the buyer. This will tell the buyer the condition of the house.
After the buyer receives the disclosure, they are allowed to terminate the contract within 7 days of the receipt of said disclosure. 7 days from February 5 is February 12 so this is the latest date the buyer can terminate the contract because of the fire.