Contract questions test a handful of doctrines over and over.
The essentials of a valid contract
Competent parties, offer and acceptance, consideration, lawful purpose — and for real estate, a signed writing (statute of frauds). Earnest money is NOT required; the mutual promises are the consideration.
Valid / void / voidable / unenforceable
Illegal purpose → void. A minor or fraud victim → voidable at their option. An oral land sale → unenforceable (valid between honest parties, but courts won't help). This classification question appears on nearly every form.
Counteroffers kill offers
A counteroffer rejects the original offer permanently — the seller can't later "accept" the original. The offeror may revoke any time before acceptance is communicated.
Remedies
Buyer defaults → seller may keep earnest money as liquidated damages (if the contract says so). Seller defaults → buyer's strongest remedy is specific performance, because land is legally unique.