为明确诊断,下列哪项检查为首选
A.心电图B.超声心动图C.24小时动态心电图D.心功能检查E.心导管检查
参考答案:B
染色体是成对存在的,基因也是成对存在的______.
He was educated at a local grammar school, _______ he went on to Cambridge.
A.from which
B.after that
C.after which
D.from this