It's hard to sift out the truth from the lies in this case.这种情况下真相和谎言很难分辨。It is often difficult to distinguish clearly between fact and fiction in this book.读这本书经常很难分辨其中的真实和虚构内容。Sometimes it's hard to tell whether illnesses result from bacteria or viruses.有时候很难分辨疾病到底是细菌引起的还是病毒引起的。