It was until dark ___ he found ___ he thought was the correct way to solve the problem.
The genetic engineering, ______ progress has been very rapid recently, is perhaps the most important of all the sciences.
I don't think the experiment is _____ failure. At least we have got _____ experience for our future work on _____ nature.
---- My neighbor plays loud music late at night. ---- ________.You really should talk to him about it.
The meeting ________ tomorrow is very important.
Although this ______ sound like a simple task, great care is needed.