7) D

From floor 11, the nearest floor is 15. This is a difference of 4 (15 – 11) floors. It takes 3 seconds to move from one floor to consecutive floor. 
So total so far is 3 x 4 = 12 seconds

From floor 15, 6 and 24 are equally close to each other. However, previously, the lift moved from 11 to 15, so it is travelling upwards. Therefore, floor 24 is the preferred floor for the lift. It takes 9 x 3 = 27 seconds to do this.
So total so far is 39 seconds.

From floor 24, the lift will go to floor 6. This will take 18 x 3 = 54 seconds.
Total = 54 + 39 = 93 seconds

From floor 6, it will go to floor 4. This will take 6 seconds.
Total = 99 seconds.

However, the lift has stopped on 3 floors before opening at floor 4. These are floors 6, 15 and 24. We must 9 seconds for each floor. This is 27 seconds.

Total = 99 + 27 = 126 seconds

So D is the answer.