________ the calculation is right, scientists can never be sure that they have included all variables and modeled them accurately.
His laziness ___________ his failing in the exam.
As we all know, smoking ___________ people’s health.
_____ you have worked out the first problem, you may go on to work on the second.
Most of the evidence was destroyed in the fire. _____, it would be almost impossible to prove Jim guilty.
_____ life exists on any other planet in the solar system still remains a question.