Answer is A-photosystem II
Answer:
Muscles work in pairs to move a bone.
Skeletal muscles only PULL in one direction. For this reason they always come in pairs. When one muscle in a pair contracts, to bend a joint for example, its counterpart then contracts and pulls in the opposite direction to straighten the joint out again.
The thing that they have in common is that they are all non metals
Equal is the answer
Hope this helps
