When the plane flies very high ,Henry can stand up and walk around .He can also read books ,newspapers or see films .The
问题描述：
When the plane flies very high ,Henry can stand up and walk around .He can also read books ,newspapers or see films .The air hostess will bring him food and drink.Henry can enjoy the flight and arrive home soon.里面的动词用flies 为什么flies 不是用fly
答
主语是3单