—Got your driving license?

—No. I ________ too busy to have enough practice, so I didn't take the driving test last week.

A．was

B．have been

C．were

D．had been

下列关于胎儿成熟度的判定，正确的是（）

A.羊水卵磷脂比鞘磷脂值（L/S比值）≥2，提示胎肺成熟

B.羊水肌酐测定＝88.4μmol/L为肾成熟

C.羊水中淀粉酶值＜450μ/L，提示胎儿唾液腺已成熟

D.羊水脂肪细胞出现率＜10%示胎儿皮肤成熟

E.超声波测胎头双顶径＝7.5cm，提示胎儿成熟