Can someone tell me what is the meaning of "lets indulge this"

Let's injoy this? hope it helps

Explanation:

to indulge is to allow ones self to enjoy the pleasure of

a,b,d are the three sentences that use a reflexive pronoun

the following key ideas correctly express the key sentence.

restate key idea: most people can learn to swim in ten short lessons.

restate key idea: the majority of water-accident victims require mouth-to-mouth breathing.

restate key idea: an empty, tightly closed gallon jug will support a tired swimmer.  

restate key idea: first aid is to prevent accidents as well as assist in rescue.

explanation: the key idea needs to have the same topic as the key sentence (drowning and safety).