Answer:
It would most likely be 3!
Step-by-step explanation:
A scientist taking photos of the stars would be using those photos as a sort of documentation. The only reason to record this is for data or research purposes, meaning that 1 and 2 are incorrect. While 4 is a possibility, it is a fruitless endeavor, as even if you managed to count all the stars in the night sky at one point, it would completely discount every star not visible from that part of the globe, making the data false/pointless. Again, this is just my educated assumption, but I do think the answer is 3. Good luck :D