The correct answer is: A. Lesser of 200 mm and 12t.
The maximum pitch of rivets in compression is the distance between the centers of two adjacent rivets in a row. The pitch is limited to ensure that the rivets are not overloaded and that the joint is strong enough to withstand the applied loads.
The IS Specifications (IS 800-2007) for riveted joints state that the maximum pitch of rivets in compression is the lesser of 200 mm and 12 times the thickness of the thinnest outside plate or angle. This means that the pitch should be no greater than 200 mm, or 12 times the thickness of the thinnest plate or angle, whichever is less.
Option A is the correct answer because it satisfies the IS Specifications. Option B is incorrect because the maximum pitch is limited to 200 mm, not 250 mm. Option C is incorrect because the maximum pitch is limited to 300 mm, not 320 mm. Option D is incorrect because the maximum pitch is limited to 300 mm, not 240 mm.