如图,在菱形ABCD中,∠ABC=60°,AB=1,E为BC的中点,则对角线BD上的动点P到E、C两点的距离之和的最小值为( )
吸烟有害健康.吸烟时产生一种能与人体血液中的血红蛋白结合的有毒气体是( )
Spring is coming. Everything seems to be l____, such as new green trees, beautiful flower and warm sunshine.