Option 1: Chandragupta

There is no evidence or historical records that suggest Chandragupta, the first ruler of the Mauryan Empire, wore trousers or was depicted in images wearing trousers.

Option 2: Ashoka

Similarly, there is no evidence or historical records that suggest Ashoka, the third ruler of the Mauryan Empire, wore trousers or was depicted in images wearing trousers.

Option 3: Kanishka

Kanishka, the ruler of the Kushan Empire in the 2nd century CE, is considered to be the first Indian ruler to be shown in images as wearing a dress akin to trousers. The portrayal of Kanishka wearing trousers could be attributed to the influence of Central Asian fashion and cultural exchanges during his reign.

Option 4: Samudragupta

There is no evidence or historical records that suggest Samudragupta, the fourth ruler of the Gupta Empire, wore trousers or was depicted in images wearing trousers.

The correct answer is Option 3: Kanishka, as he is the first Indian ruler to be shown in images wearing a dress akin to trousers, possibly due to Central Asian influences.