1.Last year,the average salary increase for poultry research assistants was 2.5%.Of the 10,000 poultry research assistants,2,000 received raises in excess of this amount.The odds that a randomly selected poultry research assistant received a salary increase in excess of 2.5%are:

　　A.20%.

　　B.1 to 5.

　　C.1 to 4.

　　solution：C

　　For event E,the probability stated as odds is P(E)/[1-P(E)].Here,the probability that a poultry research assistant received a salary increase in excess of 2.5%=2,000/10,000=0.20,or 1/5 and the odds are(1/5)/[1-(1/5)]=1/4,or 1 to 4.