被毒蛇咬伤后,应()
A、用止血带或绳子在伤口下端勒住
B、减少活动,防止血液加速流动
C、迅速跑向医院求救
D、用绳子死死捆扎伤口上端,不必松开
参考答案:B
A.Because nearly 1,000 million acres of land was burned off.
B.Because natural resources are being used up.
C.Because animals and plants are in danger of extinction.
D.Because natural beauty of the land would be ruined.
离散时间序列x(n)=sin的周期是()。
A.3
B.6
C.6π
D.非周期