Table: ar15_variants
Columns: colt_model_no
name
stock
fire_control
rear_sight
forward_assist
case_deflector
barrel_length
barrel_profile
barrel_twist
hand_guards
bayonet_lug
muzzle_device

Question: What is the rear sight in the Cole model no. 735?
SQL: SELECT "rear_sight" FROM ar15_variants WHERE "colt_model_no" = '735'

Question: What are the Colt model numbers of the models named GAU-5A/A, with no bayonet lug, no case deflector and stock of 2nd generation? 
SQL: SELECT "colt_model_no" FROM ar15_variants WHERE "bayonet_lug" = 'No' AND "stock" = '2nd Generation' AND "case_deflector" = 'No' AND "name" = 'GAU-5A/A'

Question: What's the type of muzzle devices on the models with round hand guards?
SQL: SELECT "muzzle_device" FROM ar15_variants WHERE "hand_guards" = 'Round'