It took him a long time to ______ the skills needed to become a professional artist.

A．acquire

B．inquire

C．Require

D．request

在日常生活中，我们会遇到许多种酸，例如：胃液里含有__________，食醋里含有__________，汽水里含有__________，发酵后的牛乳里含有__________。