a. You can't rely on things being done for you. absolutely
My problem here is that I think one generally relies on people not things...
In the sentence above, things are not being relied on. The sentence means that you can't rely on other people doing things for you. (it could even include machines doing things for you)
"things being done" is passive.
And we do rely on things every day: cars, bicycles, stoves, telephones, etc.