KOLKATA, India — South Africa took three wickets in the first session on Saturday on the second day of the first cricket test against India, leaving the hosts on 138-4 at Eden Gardens.Skipper Shubman Gill also retired hurt to compound India’s problems on an increasingly tough wicket, and it still trailed by 21 runs. South Africa was bowled out for 159 runs in its first innings on the first day, with Jasprit Bumrah taking 5-27.Ravindra Jadeja (11 not out) and Dhruv Jurel, on 5, were batting at the lunch break.K.L. Rahul and Washington Sundar negotiated the first hour of play without any further loss after starting the day at 37-1. The pair added 38 runs in 14 overs, scoring at a fair clip as the ball was still hard.After the drinks break, though, South Africa struck three times in the second hour of play to even things out even as India scored 101 runs in the session. Sundar was the first to go — out caught at slip off Simon Harmer who found ample help from the pitch. Sundar scored 29 runs off 82 balls, with two fours and a six.Skipper Gill retired hurt …