a) effective diameter of rivets = rivet hole diameter
b) effective diameter of rivets = nominal diameter of rivet

c) effective diameter of rivets = 1.5 x rivet hole diameter

d) effective diameter of rivets = 1.5 x nominal diameter of rivet

Answer: b
Explanation: Effective diameter of rivet is taken as rivet hole diameter instead of nominal diameter of rivet. Rivet hole diameter is diameter of rivet + clearance.