大学英语： Once是连接词，表示一旦

A thoroughly understood problem is well started toward solution. Be well started toward 是什么的良好开端。

　　3. The development of industry has also brought about large numbers of problems which have to be solved.

　　4. Related questions  相关问题；unanswered questions  为回答的问题；controlled conditions  被控制的条件

　　5. Reliable（adj.可信赖的）-unreliable（adj.不可信赖的）

　　6. Should the observations or predictions turn out to be as expected， the scientist has added confidence in the probable truth of his hypothesis. = If the observations or predictions should turn out to be as expected， the scientist has added confidence in the probable truth of his hypothesis