正常生产时，精馏塔釜温度升高的主要因素有哪些？
参考答案：
①加热蒸汽量过大。
②回流量小。
③塔釜液位过低。
④塔顶冷凝器冷却剂量小，回流温度高。
Justin kicked the ball into his own goal. It was _____ his stupid kick that we won the game.
A．because
B．since
C．thanks to
D．according to
对生物显微镜物镜转换器的精确度要求不包括（）。
A、同轴
B、齐焦
C、等高转换
D、变宽等距
