Correct option is C
Magha Saptam Mela is celebrated during the Magha month of the Hindu calendar, which corresponds to February in the Gregorian calendar. It is a sacred bathing festival observed with rituals on the seventh day of the bright half of Magha.
Explanation of options: (a) ✘ January marks the start of Magha, but the Saptami (7th day) often falls in February. (b) ✘ April is far beyond the Magha month; unrelated to the festival timing. (c) ✔ February matches the lunar calendar placement of Magha Saptami. (d) ✘ March corresponds more to Phalguna month, not Magha.