Sightseeing in this city is best done _______ by tour bus _______ by bicycles, you must choose one.
A:neither, or
B:either, or
C:both, and
D:neither, nor
一数学兴趣小组来到某公园,准备测量一座塔的高度.如图,在A处测得塔顶的仰角为α,在B处测得塔顶的仰角为β,又测量出A、B两点的距离为s米,则塔高为____米.