热传播有（）三种途径。
A、热输送
B、热传导
C、热对流
D、热辐射
参考答案：B, C, D
We _____ finish it ahead of time, though it was such a tough task.
A. could B. would C. were able to C. ought to
在数据库中，建立视图的命令是（）
A.CREATE SCHEMA命令
B.CREATE TABLE命令
C.CREATE VIEW命令
D.CREATE INDEX命令
