I´d be grateful if the colleagues could kindly help me. The exercise is to choose the item that is not gramatically possible, as follow: Do that.... a) and you´ll regret it. b) if it´ll help´. c) if you´ll get the opportunity d) - we´ll lose business The answer key proposes the wrong one as letter "c". Is that ok? What makes "b" different from "c" once both are in future?