Answer: The right answer is the A) Practican.
Explanation: Just to elaborate a little on the answer, it can be added that the subject in this sentence is plural, so options C and D should be easily discarded, since they refer to the third and the first person singular, respectively. Option B does refer to the third person plural, but it is in the subjunctive mood, and it is not correct to use it here—the sentence should say "Es importante que los atletas practiquen mucho..." Since this sentence is a fact, the best choice is option A, since the verb has been conjugated in the Present Simple: Athletes practice very much in order to improve their skills.
