—Did you catch the early bus this morning?

—No. It had left the stop________I arrived there.[ ]

A. as soon as  

B. as the time

C. by the time  

D. during the time

锡焊焊铝制件困难，关键是铝材表面极易生成氧化膜且（）。

A.速度很慢

B.速度较慢

C.速度较快

D.速度极快