湖南洞庭湖区曾经是感染血吸虫病的高危区，人若进入含有钉螺的水域，就很可能被感染血吸虫病。其中血吸虫、钉螺所属的动物类群分别是（　　）

    I really love football. I' m a member (成员) of our school football team (队) and I play four times a week. I also like swimming and I go swimming after school. I don't like basketball.

                                                                        Jack

    My favourite sport is basketball. I also like table tennis, but I don't play it at school. I go to a club (俱乐部) with my friends. I' m not very good at football.

                                                                        Anna

    Bicycle riding (骑自行车) is my fav0urite sport. I go to school by bicycle. I also like travelling (旅游) by bicycle and I-do it with my father. It's very interesting. I don't like football or" basketball.

                                                                     David

    I like football. It's really interesting. My two brothers are in our school football team and they help me. I don't like playing it with my friends.
                                                                    John.

撒哈拉沙漠是世界上最大的沙漠。