It started to snow at $10$am and at that time my garden thermometer registered $1$$^{\circ}\text{C}$.  I checked the thermometer an hour later and found that the temperature had fallen by half of a degree.  If the temperature continues to drop by half of a degree every hour what is the temperature at $6$pm? 
选项为:A:$--3$$^{\circ}\text{C}$  B:$--7$$^{\circ}\text{C}$  C:$--4$$^{\circ}\text{C}$  D:$5$$^{\circ}\text{C}$  E:$--5$$^{\circ}\text{C}$  请回答其中一个选项.