[单项选择]His interest in music dates back to his childhood, when he used to listen to his father playing the piano．
A. 他小时候对音乐非常感兴趣是由于那时他常常听父亲弹钢琴。
B. 他对音乐的兴趣源于童年时代，那时他就常常听父亲弹钢琴。
C. 他童年时代就习惯于听父亲弹钢琴，那时开始对音乐产生了兴趣。
D. 他在童年时代就习惯于听父亲弹钢琴，常常沉浸在充满着音乐的好时光里。

The relationship between human and dog dates back to at least 8,000 years ago. Different types of dogs were {{U}} (47) {{/U}} for different tasks:the ancient people in west Asia, for example, trained greyhounds (灰狗)to {{U}} (48) {{/U}} wild asses; in medieval manuscripts, illustrations of hunting scenes show terriers(猎犬) {{U}} (49) {{/U}} rabbits.
Recent research shows that dogs {{U}} (50) {{/U}} another useful function: they keep us healthy. People who have any sort of pet are more likely to {{U}} (51) {{/U}} heart attacks ( blood pressure rises when we talk to one another whereas it drops when we pat a pet). Dog owners in particular show considerably {{U}} (52) {{/U}} self-esteem and a 50% reduction in minor health problems only ten months after acquiring their pet.
In the UK, thousands of people visit the annual dog show, "Crufts", held in London. This show receives wide national and international media {{U}} (53) {{/U}}, Fi