The doctor said jokingly that his own infection of the virus _______ the discovery of a vaccine (????)of the disease.

   A. stood for           B. called for         C. paid for        D. contributed to

The doctor said jokingly that his own infection of the virus _______ the discovery of a vaccine (疫苗)of the disease

1. A.
   stood for
2. B.
   called for
3. C.
   paid for
4. D.
   contributed to

 The doctor said jokingly that his own infection of the virus _______ the discovery of a vaccine (疫苗)of the disease.

   A. stood for           B. called for         C. paid for        D. contributed to

The doctor said jokingly that his own infection of the virus _______ the discovery of a vaccine (疫苗)of the disease.

   A. stood for           B. called for         C. paid for        D. contributed to

The doctor said jokingly that his own infection of the virus _______ the discovery of a vaccine (疫苗)of the disease.