Dear Grandpa,
How are you those days? I have been missing you very     
much after I went to college a year ago. Whenever I think of     
the old days, I feel very happily. I still remember when I          
was child, you always held me in your arms and told me stories    
till I fall asleep. We often went to the fields to enjoy the pleasant    
view there. You told me the name of different plants and their     
characteristics. Gradually, I became interesting in biology        
and chose to learn biology when I entered into the college. Now   
my friend Ann, together with me, are going to do field study      
and the findings will be use as materials for our research. Since  
we"ll do the study in our hometown, I hope to see you by then.
                                              Yours,
                                              Daisy

A. why                      
B. that
C. when                      
D. where