某些表型正常的母亲实际是21三体细胞很少的____,如果其____细胞中____21三体细胞,她们的子女就有可能遗传获得额外的21号染色体,特别是较年轻的、有过]个以上的21三体型孩子的母亲。
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1963年由Lqjeune-等首先报道,因患儿具特有的____哭声,故又称为____。
His oral English is _____ than his brother's.
A. well
B. good
C. better
D. fine
I would rather _____ a job and earn money.
A. to find
B. finding
C. found
D. find