考题求助~

In a blow to those who still harbored the illusion that E-mail exchanges are private, a watchdog group recently uncovered a trick for enabling an interloper to rig an E-mail message so that this person will be privy to any comments that a recipient had added as the message is forwarded to others or sent back and forth.

• who still harbored the illusion that E-mail exchanges are private, a watchdog group recently uncovered a trick for enabling an interloper to rig an E-mail message so that this person will be privy to any comments that a recipient had added
• who had still been harboring the illusion that E-mail exchanges are private, a watchdog group recently uncovered a trick for enabling an interloper to rig an E-mail message so that this person was privy to any comments that a recipient might have added
• who still were harboring the illusion that E-mail exchanges are private, a watchdog group recently uncovered a trick enabling an interloper to rig an E-mail message so that this person is privy to any comments that a recipient would add
• still harboring the illusion that E-mail exchanges are private, a watchdog group recently uncovered a trick that enables an interloper to rig an E-mail message so that this person will be privy to any comments that a recipient might add
• still harboring the illusion that E-mail exchanges had been private, a watchdog group recently uncovered a trick that will enable an interloper to rig an E-mail message so that this person was privy to any comments that a recipient might add

这题我就只靠着trick for enabling vs trick that enables和时态来排除的，这句话从句子成分上可以怎么判断么？我感觉好像都差不多