Step 1: Think about what happened on 13 April 1919.
That date is fixed in memory as the Jallianwala Bagh Massacre, where General Dyer's troops fired on an unarmed crowd gathered for Baisakhi in Amritsar, Punjab. So place (A) is Amritsar.
Step 2: Recall the 1927 Congress session.
The Indian National Congress met in 1927 at Madras, presided over by Dr M.A. Ansari, and this session decided to boycott the all white Simon Commission. So place (B) is Madras, known today as Chennai.
Step 3: Mark both places on the map.
Amritsar sits in the north in Punjab, and Madras or Chennai sits on the southeastern coast, so both should be marked at their respective locations.
Final answer, place (A) is Amritsar and place (B) is Madras (Chennai).