炉膛负压过大是由于（）开度太大，使炉膛负压增加。
A、快开门
B、风机
C、烟道挡板
D、风门
参考答案：C
His father likes keeping dogs and .
A．his mother likes so
B．so his mother
C．so his mother does
D．so does his mother
炭黑用量较多的胶料可采用（）
A、一段混炼
B、混炼
C、分段混炼
D、二段混炼
