①不仅履行了道德义务，也履行了法律义务

②是关爱他人、服务社会、奉献社会的行为

③是履行社会责任，不计代价与回报的行为

④拯救了他人生命，提升了自己的生命价值

一辆执勤的警车停在限速v_m=90km/h公路边，当警员发现从他旁边以v=20m/s的速度匀速行驶的摩托车由违章行为时，立即决定前去追赶；经t₀=2s警车发动起来，以加速度a=2m/s²做匀加速运动，试问：

   Height is just one of the thousands of features your genes decide. In fact, because you have two parents, your genes provide you a height that usually lands somewhere between the height of each parent. If both your parents are tall, then most probably you will be tall, too, but if you have questions about how tall you're going to be, ask your doctor if he or she can help you find it out.
    But genes don't decide everything. For example, eating an unhealthy diet can keep you from growing to your full potential(潜力). Getting plenty of sleep and enough exercise will help you grow to the expected height.
    No doubt you're wondering how fast you should grow. It depends. There's no perfect or right answer. Generally speaking, kids grow about 2 inches (6 centimeters) a year between age 3 and the time when they start puberty (when your body starts changing and becoming more grown up).
    Your doctor will know how your growth has been going over the years. Two centimeters here and 2 inches there are not nearly as important as the height you're at now, how you've been growing up to this point, and what other changes your body may be going through.
    Don't be scared if you seem to have grown a lot in a very short time. Everyone has a growth spurt（高峰）during puberty. The age for starting puberty is about 10 for girls and about 11 for boys. But it can be earlier or later ----between 7 and 13 for girls and 9 and 15 for boys.
    You'll usually begin to notice that you're growing faster about a year or so after your body starts to show the first changes of puberty.

读下列材料，回答问题。

材料一　下图是“我国东部沿海某大城市示意图”，统计显示近年来有数十万人迁入该城市。

材料二　雨水收集系统是将雨水收集并进行处理后达到使用标准的系统，主要收集屋顶雨水和地面雨水。在目前我国水资源紧张、水污染加重、城市内涝加剧的情况下，将雨水收集并利用势在必行。