Pitch of tacking rivets, when double angles connected back to back and acting as tension members should not be more than A. 500 mm B. 600 mm C. 1000 mm D. 300 mm

The correct answer is D. 300 mm.

The pitch of tacking rivets, when double angles connected back to back and acting as tension members should not be more than 300 mm. This is to ensure that the rivets are able to hold the two angles together and prevent them from pulling apart. If the pitch is too large, the rivets may not be able to provide enough strength and the angles may come apart.

The other options are incorrect because they are too large. A pitch of 500 mm would not be strong enough to hold the angles together, and a pitch of 600 mm or 1000 mm would be even weaker.