下列分子式哪个不正确:()?
A.CaHCO3
B.Na2CO3
C.NaNO2
D.NaHCO3
参考答案:A
在竖直地面上以速度2v0竖直上抛一物体A后,又以初速度v0从同一地点竖直上抛另一物体B,若要使物体在空中相遇,则两物抛出的时间间隔Δt的取值不可能为(不计空气阻力)
—The weather isn't good enough for an outing,is it?
—Not at all. We can't have ________ at this time of the year.
A.a worse day
B.a nicer day
C.such bad a day
D.so fine a day