All three work for me.
This morning I got a question from a student of mine. Though I gave the correct choice as "C". I failed to make a proper explanation to "WHY NOT A?" Here is the question for your considerations
.................. in case they lose their way.
A)The campers will carry a map with them,
B)Some of the tourists are planning to hire a guide,
C) Travellers planning to trek in the mountains are advised to take a local guide with them
Thanks for your time.
I'd say it's the punctuation, though it seems harsh to me, but I wouldn't use the comma in A) or B).
I like A best.
If they take a guide with them there's no chance of them losing their way.