Muscles move bones by relaxing against them pushing them pulling them stretching back and forth

I dont know the answer but I do know that one of the wrong answers is stretching back and forth.

I put that as my answer when i took the test and it was wrong

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.

in a chemical reaction, the atoms and molecules produced by the reaction are called products. no new atoms are created, and no atoms are destroyed. in a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.