What is most likely the author’s reason for mentioning the State of the Union in the first line of the address? 1st line: Ladies and gentlemen, I’d planned to speak to you tonight to report on the state of the Union, but the events of earlier today have led me to change those plans. Question 5 options:
A) to make it clear that he just came up with these remarks on the spot
B) to tie in the Challenger explosion with the rest of his planned remarks for the State of the Union
C) to emphasize the historic nature of the tragedy that occurred
D) to vent his frustration at the change of plans

The mention of the change of plans was most likely intended to emphasize that the nature and scale of the disaster was of historic proportions and warranted being addressed during the State of the Union speech.

While the passage does not say if the whole State of Union address was postponed or not, what is clear is that the President goes on to talk about the Challenger disaster and most probably dedicates the entire speech to the fateful incident.