Really would appreciate if someone could me on 18 19 20 and 21

The population of unionid mussels decreased after zebra mussels were introduced. zebra mussels competed with the unionid mussels for food. the zebra mussels were able to displace the unionid mussels, allowing the zebra mussel population to increase  over the years. the unionid mussel population decreased because  of lack of food.

The answer to the question: choose the correct statement.  a) when ethane reacts with fluorine gas the product is less stable.b) addition reactions of unsaturated hydrocarbons and halogens requires a high activation energy.  c)the double covalent bond within unsaturated hydrocarbons requires a lot of energy to break.  d)the double covalent bond within unsaturated hydrocarbons can be broken easily.is: a) when ethane reacts with fluorine gas the product is less stable.

H+ + cn– + li+ + oh– mc001-4.jpg li+ + cn– + h2o