1.China's population ( )smaller in the past ( )now.2.Cars ( )slower in the past now.

1.China's population ( )smaller in the past ( )now.2.Cars ( )slower in the past now.
1.China's population ( )smaller in the past ( )now.2.Cars ( )slower in the past now.

1.China's population ( )smaller in the past ( )now.2.Cars ( )slower in the past now.
1.China's population ( was )smaller in the past ( than it is ) now.
2.Cars ( were ) slower in the past (than they are ) now.
要是每空只能填一词,后面的 it is 和 they are 也可以省略.