Select the phrase that best completes this sentence. es importante unidamente a.. proteger el medio ambiente b. contaminar el agua c .degradar el suelo d. calentar océanos

The right answer is the A) proteger el medio ambiente.  

Explanation: Just to elaborate a little on the answer, it can be added that the other options are not appropriate, since they refer to negative and damaging actions (contaminating the water, degrading the soil, and warming the oceans), so they should not be considered important. The right option is, therefore, the first one: "It is important to protect the environment all together."