Which of the following statement(s) best explain why the SID…

Which of the following statement(s) best explain why the SID may be higher than 40 inches for the lower leg projections. 1. When a 7 X 17 LW IR is being used. 2. To expose all of the IR when it is used diagonally because the collimators do not open up past 17 inches. 3. To expose all of the IR when it is used diagonally. 4. The collimators do not open up past 17 inches. 5. All statements are correct.