下列句中均有一处错误,指出并改正! the weather of xi'an is colder than that o

下列句中均有一处错误,指出并改正! the weather of xi'an is colder than that of haikou
china is larger than all countries in africa
she is the tallest of the four girls
when you learn the piano, you'll find it not difficult if practicing a lot
the birthday cake tasted so good that it was eaten up quickly
the more careful you are, the fewer mistakes you'll make
which jacket do you prefer, the red one or the blue one?
i'm sure you'll have a wonderful time