问题详情：
根据句意和汉语注释，写出单词的正确形式。
uncle started to learn swimming in her __________(四十).
is now a manager while his twin brother___________(保持不变) a worker.
useful the ___________ sound! I think he will take them.(建议)
’t be too _________ about your son is old enough to look after himself.(担心)
【回答】
1. forties 2. remains estions ied
知识点：单词拼写
题型：单词拼写