在以下选项中,表示反向选择的正则表达式的是______。
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对于字符串$1688,在以下命令中,能原样输出$1688的是______。
A. '$1688'
B. "$1688"
C. `$1688`
D. /$1688
对于字符串echo echo everybody,在以下命令中,能将其作为命令执行后返回的是______。
A. 'echo echo everybody'
B. "echo echo everybody"
C. `echo echo everybody`
D. \echo echo everybody
对于变量PRICE,其值为1688,执行以下命令中,能输出字符串$1688的是______。
A. echo '$PRICE'
B. echo "$PRICE"
C. echo `$PRICE`
D. echo \$$PRICE
After I _______ for an hour, I realized that he was not coming.
A. was waiting
B. had been waiting
C. waited
D. have waited