The correct option is B Is played
The simple present tense expresses a general truth, habit or routine.
In the given sentence, the phrase 'at this time' suggests a routine or daily habit.
This means that the sentence is in simple present tense. The players play tennis every day at one particular time "at this time". Hence, the correct verb must be in simple present.
Option C: 'Is played' is in the simple present tense. It describes the action 'to play tennis' to take place every day at a specific time "at this time". Hence option C is correct.
Options A and D: 'Are' in 'are being played' and 'are played' refer to a plural noun. But, 'tennis' is the name of a game; it does not have a plural form.
Option B: 'Is being played' refers to the present continuous tense. It describes an action that is happening at the present, 'now'. But, the adverb 'now' isn't present. 'At this time' does not refer to an action happening 'now'.
Hence options A, B and D are incorrect.