Correct answer is (d) lug angles and their connection to gusset should be capable of developing a strength of not less than 20% of excess of force of outstanding leg of angle
The best I can explain: In case of angle members, lug angles and their connection to gusset should be capable of developing a strength of not less than 20% of excess of force of outstanding leg of angle, and the connection of lug angle to angle member should be capable of developing a strength of 40% of excess of force.