Pls answer quickly the spring scan shows mass in kilograms what is the mass shown here?

A) 2.5kg

B) 7.5kg

C) 12.5kg

D) 17.5

Scores on the cognitive scale of the bayley-scales of infant and toddler development range from 1 to 19, with a standard deviation of 3. calculate the margin of error in estimating the true mean cognitive scale score, with 99% confidence, if there are 12 infants and toddlers in a sample.