The dog is _____ the chair.
A:in
B:under
C:at
A: What would you like?
B: ________________()
如图1,为美化校园环境,某校计划在一块长为60米,宽为40米的长方形空地上修建一个长方形花圃,并将花圃四周余下的空地修建成同样宽的通道,设通道宽为a米.