The swimming pool is _______ only in summer. So you can't go there now.[ ]

A. present

B. available

C. precious

D. convenient

出现Cheyne-StOkes和Biots呼吸最主要的机制为

A．胸部外伤呼吸受抑制
B．胸腔积液呼吸受抑制
C．呼吸中枢兴奋性降低
D．呼吸肌麻痹
E．严重神经衰竭