I have stayed in the UK for a year (2017-18) during my postgraduate study? Though my purpose of the visit was purely educational for a year long, however, I made multiple entries (3 times) including a study trip to Brasil and trip to my home country during Easter break. I will visit again for the graduation ceremony to be held in December. Now I am applying for the standard visitor visa again and am confused about the answer for "How many times have you been to the UK in the last 10 years?" with options - (a) 0, (b) Once, (c) 2-5, (d) More than 6.
Option C (2-5)
That’s what you just told us, tell the same to UKVI as well.
They will know about your previous visas and it’s up to them to decide how to assess the answers, you just answer to the best of your knowledge and you don’t have to worry about your truthful answers meaning something else.