(2) The feeding conditions of rats in Group A and Group B are the same, except that "Group A is placed in front of the computer that is not turned on, and Group B is placed in front of the computer that is turned on", which can form a group of control experiments, and the variable is whether the computer is turned on or not;
(3) Using 8 rats instead of/kloc-0 in each experimental group can eliminate the influence of accidental factors and reduce the error;
(4) As can be seen from the data in Figure A, the weight gain of rats in Group B is small, and as can be seen from the data in Figure B, the abnormal rate of sperm in rats in Group B is high, indicating that computer radiation has affected the weight gain and normal sperm development of rats in Group B;
(5) The data show that long-term computer radiation is harmful to the health of mice, and it is also very harmful to human health, especially to middle school students. Long-term use of computers is not only a waste of time, but also radiation pollution from computers will affect the circulatory system, immunity, reproduction and metabolic functions of the human body, and even induce cancer and accelerate the proliferation of cancer cells in the human body. So, don't stay in front of the computer for a long time and don't play games for a short time.
So the answer is:
(1) male rats; (2)B； (3) avoiding contingency and making the experimental results more reliable; (4)b； (5) Don't stay in front of the computer for a long time/play for a short time.