he bought a computer several months ago高一英语

it was since
since并不一定引导完成时,题目中这种说法就很常见
若按楼上的为强调句,将it was that去掉后原句不成立（这是判断强调去是否正确的方法）,而且楼上多加了一个ago
这句话换为强调句应是It was several months ago that he bought a computer.