<span>They'll / do great things if they're willing to dig</span>
No one knows the origin, perhaps used by early man to explain the glorious deeds of heroes, almost five thousand years old.
False the both are in poetry but are not the same
More effective than the other candidates, he would have been a great president when it came to negotiating with other countries. (if you talking about Bernie Sanders)
A parallel structure means that the same form of the word is used in each part of the sentence. So the correct answer is 'I look forward to visiting Phoenix and to meet Rachel'. For this sentence to be correct, it would need to say 'I look forward to visiting Phoenix and meeting Rachel'.