The correct option is A □△△□
The series is △□□△,△□□△,△□□△. Here the section ′△□□△′ is repeated in the series.
Solving steps : The candidate has to look for clues to solve such series pattern. ′□□△′ in the series indicates that ′△′ in this series is preceded by two ′□′ so, the first blank and the last blank will be filled by ′□′. Now the first set is formed, i.e., ′△□□△′ in the beginning. This set is repeated, so the second and third blanks will have ′△′ filling them.