Apretest of knowledge about microcomputers is given to a group of students 5 min prior to a filnm on the subject. a posttest given 10 min after the film showed a 10-point gain from the pretest. the researcher concludes that the film produced the gain. which of the following is likely the threat to internal validity?

a. statestical regression
b. selection bias
c, testing
d. maturation

21/58.

hope to be marked brainliest

49%

step-by-step explanation:

when you realize that you dont know just realize i just took a test and im so smart

third choice down

step-by-step explanation:

the first inequality is based on the number of adults and campers, and the second inequality is based on the cost of feeding both the adult and the camper.

we know that there is room for 525 people max.   it's ok to have less than 525, but it's not ok to have more than 525, so the inequality is less than or equal to.   the number combination of adults (x) and campers (y) cannot exceed this 525 max.   therefore:

x + y ≤ 525

now we talk about cost.   it costs $9 to feed one adult, so depending upon the number of adults you have (x) depends upon how much it will cost to feed that number of adults.   same with the campers, who cost $5 to feed.   the adults can be represented by 9x and the campers can be represented by 5y.   since the budget cannot exceed 1,200, the second inequality is:

9x + 5y ≤ 1200