Step 1: Understanding the question
We must pick which of the four films were directed by Mrinal Sen. So we match each film with its director and keep only those by Sen.
Step 2: Check A, Bhuvan Shome
Bhuvan Shome (1969) was directed by Mrinal Sen. It is often called the start of the New Wave in Hindi cinema. So A is TRUE.
Step 3: Check B, Garam Hawa
Garam Hawa (1973) is a film on the partition, directed by M. S. Sathyu, not by Sen. So B is FALSE.
Step 4: Check C, 27 Down
27 Down (1974) was directed by Avtar Kaul. So C is FALSE.
Step 5: Check D, Calcutta 71
Calcutta 71 (1972) is part of Sen's Calcutta trilogy and was directed by him. So D is TRUE.
Step 6: Match with the options
The true set is A and D. Option 1 adds B, which is wrong. Option 3 has B but misses D, so it is wrong. Option 4 has B and C, which are wrong. Option 2 has A and D only.
Final Answer:
Mrinal Sen made Bhuvan Shome and Calcutta 71, so the answer is option (2).
\[ \boxed{\text{Option (2): A and D only}} \]