Please answer the following question by reasoning step-by-step.
Given the sentence "There are groups of people in green or purple shirts gathered outside holding signs and purple balloons." can we conclude that "Group of people gathered outside to celebrate their boss birthday."?\nOptions:\n- yes\n- it is not possible to tell\n- no

it is not possible to tell
Gathering outside does not mean it is to celebrate their boss birthday.

.

So, the answer is it is not possible to tell