_____ three influenza type A virus subtypes(子类型) have been found in pigs.
—You may find the key to the math problem on page 107. —Ah, it's so simple. I wonder why I _of that.
A turning point of the continuously high housing price won't appear suddenly because there must be a certain process _many factors lead to the change.
---Ken, _, but your radio is going too loud. ---Oh, I’m sorry. I’ll turn it down right now.
When chatting with her on the mobile phone, the battery _dead suddenly.
His explanation that he was at loss what to do next doesn't hold water.