1. Modal verb for possibility: "rewards can be really effective" uses the modal verb "can" to express possibility and general truth, which is common in spoken English.
2. Conditional structure: "When a child receives praise or a small prize for their efforts, it not only motivates them..." uses a conditional clause to show cause and effect, making the answer more logical and connected.
3. Parallel structure: "not only motivates them to keep trying but also helps them understand..." uses parallelism, which makes the sentence clearer and more fluent.
4. Present simple tense: The answer consistently uses the present simple tense ("receives," "motivates," "helps," "boost," "encourage," "makes") to talk about general truths and habitual actions, which is appropriate for this type of question.