溶液冰
参考答案:是指由共晶溶液冻结成的冰,其熔化温度一般在0℃以下。
He did well in the examination. He _____ hard at his lessons..
A.must have worked
B.can have worked
C.will have worked
D.has worked
关于经线和经度的叙述,正确的是()
A.同一经度,纬度越高,越在北方
B.春秋分日,同一经线上同时日出日落
C.东经20°与西经20°经线区时相差2h,地方时相差2h40min
D.因每条经线的长度相等,故不同纬线上经度相差1°的弧长均是相等的