—I have been waiting for you so long. —Sorry, I have been in the library, _______ my friend look for some books.
The advanced entire production process is paperless and much faster than that of ______ factories.
Her parents’ quarrelling with each other _________ is the main cause of her family’s breaking up.
Eco-environment Tayshaun has endeavored not to ________ on environmental protection during industrial development.
The virus Ebola is reported ______ over 3,000 lives in 5 countries of West Africa by now.
It is generally believed that communication skills are becoming ______ it takes to be a good doctor.