Answer: Option (a) is the correct answer.
Step-by-step explanation:
Conservation efforts means to carefully preserve or protect something. These efforts are fruitful when a majority of people or communities come together in order to preserve something good for the betterment of environment.
As when maximum number of people come lend their hands for help only then conservation efforts can be achieved.
For example, a city with maximum pollution can only be conserved when maximum groups of people decide to conserve plants or plant more number of trees.
Thus, we can conclude that conservation efforts are most effective when conservation efforts are most effective when multiple groups cooperate.