“人与生物圈计划”的实施,最重要措施为 [ ]
A.维持自然界的生态平衡
B.协调人与生物圈的关系
C.建立生物圈的自然保护区
D.实施“人类基因组计划”
答案:C
Have you ever ___ to the museum ___ we paid a visit last year?
A.been; which
B.been; to which
C.gone; which
D.gone; to which
板块