At home, he keeps some pets, to which he devotes all his spare time.
他家里养着一些宠物，他把所有的空闲时间都花在养宠物上面了。
During sleep, the number of sites to which adenosine is bound decreases.
在睡眠期间，腺苷结合的位点数量减少。
At issue is the extent to which exam results reflect a student's ability.
考试成绩能在多大程度上反映学生的能力是问题的焦点。