An import threshold for mercury in crayfish is 9 parts per billion (ppb). A study obtained a random sample of 120 crayfish from a large lake. Of these, 24 have levels of mercury that exceeded 9 ppb. Past research had shown that 25% of the crayfish had levels that exceed 9 ppb. The researchers wanted to see if there was a change in contamination in crayfish. What is the test statistic for this problem? (use 2 decimal places)?
A. -1.26
B. -1.37
C. 1.26
D. -.31