1.
如图,C为线段AE上一动点(不与A、E重合),在AE同侧分别作等边△ABC和等边△CDE,AD与BE交于点O,AD与BC交于点P,BE与CD交于点Q,连接PQ,以下五个结论:①AD=BE;②PQ∥AE;③CP=CQ;④BO=OE;⑤∠AOB=60°,恒成立的结论有( )
| A. | ①③⑤ | B. | ①③④⑤ | C. | ①②③⑤ | D. | ①②③④⑤ |
19.进入2016年3月份,全球的寨卡病毒病疫情愈演愈烈,寨卡病毒是一种通过蚊虫进行传播的虫媒病毒,其直径约为0.000 002 1厘米,这种病毒直径(单位为厘米)用科学记数法表示为( )
0 286583 286591 286597 286601 286607 286609 286613 286619 286621 286627 286633 286637 286639 286643 286649 286651 286657 286661 286663 286667 286669 286673 286675 286677 286678 286679 286681 286682 286683 286685 286687 286691 286693 286697 286699 286703 286709 286711 286717 286721 286723 286727 286733 286739 286741 286747 286751 286753 286759 286763 286769 286777 366461
| A. | 2.1×106 | B. | -2.1×106 | C. | 2.1×10-6 | D. | 0.21×10-5 |