1.The students should try to learn better.同义句改写

1。 should 可以换写成 ought to 或 are supposed to2。 I often hear from my American pen friends。还可以：把 get 换写成 receive；把pen friends 换写成 pen pals。3。 necessary 或 essential4。 pull 或 draw 5。 Jim is a hard-working student, who is crazy/fascinated about studying/studies。6。 will 可以换写成 are going to；look after the animals well 可以换写成 take good care of the animals7。 Our teacher stood in front of the blackboard with a book in his/her hand/hands。8。 The twins walked along the Sixth Street/Avenue to the end。9。 a lot of 或 a number of10。 I'm looking forward to getting/receiving your letter。