多层焊时，为保证根部焊透，打底焊缝使用的焊条直径与其他层焊缝相比应（）。
A.小些
B．不变
C．大些
参考答案：A
Alu 相当序列基因
-- Would you like to come to the dinner party here on Saturday ?
---Thank you. I'd love to, _____ I'll have to finish all my homework before the weeked, otherwise, my parents won't let me go.]
A．because
B．and
C．so
D．but
