A:干旱第50天时,蓄水量为1 200万米3
B:干旱开始后,蓄水量每天增加20万米3
C:干旱开始时,蓄水量为200万米3
D:干旱开始后,蓄水量每天减少20万米3
They feel ____(内疚) about not being able to see their son often because they are busy with their work.
A blue whale can weigh ____ ____ ____ 120 tons.
声音在生活中有许多应用,用超声波能粉碎人体内的“结石”说明声波具有 ____