Some problems ___ in the lecture by Mr.Smith are very popular in our school, such as the waste of electricity, water and food, etc...
A. referring B. referred to C. referring to D. were referred
Some problems ___ in the lecture by Mr.Smith are very popular in our school, such as the waste of electricity, water and food, etc...
A. referring B. referred to C. referring to D. were referred
B
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