大堆烟煤在存储期间容易发生“（）”现象。A、风化 B、变质 C、被盗 D、自燃

根据短文内容填空，每空一词。

     For your next vacation, why not consider 1.            Paris? Paris is one of the liveliest 2.______in. Europe.   It has some fantastic3.______including the Eiffel Tower and Notre Dame Cathedral, one of the most famous4.______in the world. In 5.______ , though, France is quite an expensive place. Don't forget to enjoy the wine there !

计算3×4和4×3的口诀是（    ）。

如何繁殖下列花卉植物：大丽花、百合、蟆叶秋海棠、仙客来？

降低底片衬度可采取下列哪种措施？（）

A、增加辐射源与物体间的距离

B、尽量提高X射线管的管电流

C、尽量提高X射线管的管电压

D、尽量增加显影时间

DRIs包含4个参考值（EAR，RNI，AI，UL），都能用于群体膳食评价。