Which one is correct -<br/><br/>1) The will and the drive of these men is unbelievable.<br/><br/>or<br/><br/>2) The will and the drive of these men are unbelievable.<br/><br/>The only difference is the use of 'is' in the first sentence and 'are' in the second. Also, please tell me why it is correct and not the other.<br/><br/>Thanks in advance!