Do you know _________ at this time yesterday?[ ]

A. what she is doing

B. what is she doing

C. what she was doing

D. what was she doing

目前我国粮食污染最严重的毒素是

A．黄曲霉毒素
B．黄变米毒素
C．岛青霉毒素
D．杂色曲霉素
E．展青霉毒素