Final answer:
The sentence starting with a subordinate clause is 'When I feel stressed, I like to play on my computer because it helps me relax.' A subordinate clause cannot stand alone and provides additional context to the main clause.
Step-by-step explanation:
The sentence that starts with a subordinate clause is: "When I feel stressed, I like to play on my computer because it helps me relax." A subordinate clause is a clause that cannot stand alone as a complete sentence, because it does not express a complete thought. It is dependent on the main clause to provide full context and meaning. The subordinate clause in this sentence is introduced by the subordinating conjunction 'when', which connects the clause to the main idea. This clause provides a condition under which the main action—liking to play on the computer—takes place.