The yellow car in the picture is stopped because its driver wants to go straight ahead. According to the signage, what should it do?

Why this is the correct answer

When a traffic light shows a red main light together with a green arrow pointing right, vehicles may turn right in the direction of the arrow, regardless of the red light. They must do so with caution, yielding to vehicles already in the lane they are joining and to any pedestrians crossing. Importantly, Spanish traffic rules state that any vehicle in the lane that the arrow-directed traffic must use is OBLIGED to follow the direction of the green arrow, even if the driver originally wanted to go straight. This is because: 1. The red main light prohibits going straight. 2. Remaining stopped in this lane would block other vehicles behind (like the blue car) that wish to turn right as permitted by the green arrow. So what should you do if you want to go straight? You should have positioned yourself in a different lane before reaching the traffic light. If you are already in this lane when the green arrow turns on, you have no choice: you must turn right and then find an alternative route to reach your destination. You cannot stay stopped and wait for the green light to go straight, as this would unnecessarily obstruct traffic. Option A is wrong because simply changing lanes does not solve the problem -- the obligation is to follow the green arrow direction. Option C is wrong because the red main light does not allow going straight, and staying stopped blocks other traffic.