In the following passage some of the words have been deleted. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.

Planking is free and (1)___________ only a couple of minute - no gym membership or special equipment (2)___________ . Squatting, dead-lifting and pressing overhead without injury is hard to do without a strong (3)___________ , "We need to keep out spine straight to do these (4)___________ . Planking provides you with better core strength to be able to brace during these (5) ___________ ," Lawton says.