A:10π
B:24π
C:36π
D:48π
—We are supposed to visit him from time to time. Then he won't feel _______.
推理是一种重要的学习方法,下列推理中正确的是( )
甲乙两个婴儿参加爬行比赛,甲沿着一个边长是2米的正方形爬行一圈,乙沿着一个直径是2米的圆形爬行一圈,他们的速度一样,谁先爬行完一圈?