使用水牙线有了黑三角:Peter helped his friend to study English.(解释句子)

Peter helped his friend to study English.(解释句子) Peter helped his friend to study English.(用英语解释句子) --Mum,I helped my uncle clean his garden just now. Peter asked me to help him _____ his maths. Peter prefers to be his own boss and _____ his own boss he helped his grandma lay on her back,错在哪里？谢谢！ Peter was so angry that he hit the thief his face The key __ be Peter's.His is still in the lock.A, can't B.mustn't Peter 是谁 How much this helped 等于This helped a lot 吗