What is the best way to change the sentence below from active voice to passive voice?

expert campers advise others to bring extra batteries for the flashlight when camping.

a. you might advise someone to bring extra batteries for the flashlight when camping.
b. when camping, extra batteries should be brought for the flashlight.
c. when camping, a person might advise another person to bring extra batteries for the flashlight.
d. some people would advise you to bring extra batteries for the flashlight when camping.