—Do you know how to pronounce this word?

—Yes. I ______ in the dictionary yesterday.   [ ]

A. looked it up

B. worked it out   

C. gave it away  

D. picked it up      

当事人订立合同，要经过要约、承诺。下列文件中，构成合同要约的是（）。

A．招标公告

B．投标文件

C．宣传广告

D．招股说明书