单项选择题
A．To check the accuracy of scales. B．To calculate the density of other metals. C．To observe changes in the atmosphere. D．To measure amounts of rainfall.
A．Here and there. B．Again and again. C．As usual. D．At the same time.
A．He drives too fast. B．He plays his guitar too loudly. C．His radio wakes her children up. D．His friends are too noisy.