Can anyone tell me the answer for this -

A new study has found that college students had been more involved in on-campus political activities during the last few years than at any time the past two decades.

Options are -
i) same as the underlined
ii) had been....than at any other time
iii) have been..than at any other time
iv) have been...than at any time
v) are more involved ... as compared to any other time

I could figure out that at any other time is necessary for comparison,
but how should one decide between had been,have been and are ?