Argument no.5. the rapture takes place at the end of the tribulation period because...

the second coming and the rapture are looked upon as a single event which is called "the day of Christ"

"Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him,

That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand."

2 Thes. 2:2-3

Although two distinct events are mentioned in second verse (Christ's coming and the Rapture), they are actually described as one event - the so-called "the day of Christ".  This indicates that these two events are inseparable.

A sidenote:

It is important to note that "the coming of our Lord" refers to the actual Second Coming of our Lord to this Earth. It cannot mean the the so-called "secret return of Christ for His Church." By the context of the following verses, the "coming of our Lord" in verse 1 takes place at the end of the Great Tribulation, when Christ kills the "man of sin" (i.e. the Beast - also see Rev.19:11–21).


Although it may look insignificant, the rapture and the Second Coming are always described in this order: the Christ's Coming first, and the Rapture second. See 2 Thes. 2:2–3, 1 Thes. 4:15-17, Mat.24:30–31.


Of 1 Thes. 4:15-17 can also be noted that the event described by verse 15 is the actual Second Coming of Christ to this Earth. The verse clearly states so: "we which are alive and remain unto the coming of the Lord". This also means that, taking the verse 16 in the context of the previous 15th verse, the rapture will take place at Christ's Second Coming.