I _____swim last year. [ ] A. can B. cou_爱下问搜题

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问题选择题

I _____ swim last year. [ ]

A. can

B. could

C. can to

D. could to

答案

答案：B

单项选择题

在指定字段或表达式中不允许出现重复值的索引是

A．惟一索引

B．惟一索引和候选索引

C．惟一索引和主索引

D．主索引和候选索引

问答题

影响钙吸收的因素有哪些