射线只能对体细胞产生致畸作用，而不能对生殖细胞产生致畸作用( )。
参考答案：错
食物中毒的特点是许多人同时发病，病状相似，病情急，进展快，且都有食用某种食物的历史。
His father _____ for 2 years. [ ]
A. has died
B. has been dead
C. was dead
D. died
