意大利传教士（）是最早来到中国的外国传教士之一。
参考答案：利玛窦
— How about your travel?
— You can hardly imagine what difficulty we have had ______ the vast desert. [ ]
A. explored
B. exploring
C. to explore
D. explore
节流管汇液控箱上的调速阀用来控制液动节流阀的关开。（）
