Which of the following are correctly matched?
A.
Primary sex characteristic- the development of breasts in females
B.
Primary sex characteristic- the development of muscles in males
C.
Secondary sex characteristic- the production of sperm in males
D.
Secondary sex characteristic- the widening of hips in females

In a heat engine if 1000 j of heat enters the system the piston does 500 j of work, what is the final internal energy of the system if the initial energy was 2000 j? 1. write the equation 2.list out your known variables 3.plug the numbers into the equations 4.solve 5.write your solution statement that includes initial energy and final