pandas groupby and sort values I am studying for an exam and encountered this problem from past worksheets:

This is the data frame called 'contest' with granularity as each submission of question from each contestant in the math contest. The question is

and the answer is in red. I get why that works, but why is the 4th choice wrong? I really can't figure it out - please help.
*please let me know if this is not allowed as a post in this community.
for full description of the problem:

In this question, we will be looking at the contest dataframe which contains data from a
math contest in 2019. In the contest, each participant had a total of five questions. The participants submit each question separately and each row of the DataFrame records a particular submission of one of the contestants by some participant. The Timestamp column specifies the
time a given problem is submitted by a participant; each timestamp is discretized to the minute
and has been properly converted to a Pandas datetime object with pd.to datetime.
The Contestant column contains the id-name pair of each participant. The Question
column contains the question that was submitted. The Correct column tells us if the answer
given in the submission is correct (1) or not (0). Assume each participant can have several
submissions for the same problem, but they can only submit one question per minute.
If the participant has answered the question 2 before the question 1, you will lose the information on question one by using .agg(&quot;first&quot;) in the 4th option