Final answer:
The rectangular picture frame retains its four right angles after being slid to the right, so the answer is D. 4.
Step-by-step explanation:
The question asks about the number of right angles in a rectangular picture frame after it has been slid to the right. Moving the picture frame does not alter its shape or the angles within it. Therefore, if the picture frame had four right angles before being moved, it will still have four right angles after being moved. The correct answer to the question 'How many right angles does the picture frame have now?' is D. 4.