题目

关于函数有下列命题：①函数的周期为；               ②直线是的一条对称轴；③点是的图象的一个对称中心；④将的图象向左平移个单位，可得到的图象．其中真命题的序号是       .（把你认为真命题的序号都写上） 答案：①③．句型转换。1. You are supposed to write quickly.（对画线部分提问）                                      to write?2. I was used to eating with spoons.（改为一般疑问句）                                             with spoons?3. Tom is good at math, and he is good at French, too．（改为同义句）    Tom is good at    math    French.4. I saw him take your umbrella.（改为被动语态）  He                                  your umbrella.5. Chinese is the most important subject of all.（改为含有比较级的句子）    Chinese is                                                        .