seasonality question from Schweser (level 2 quant) understand, regarding, somebody, question, problems

cfalevel2011

I have a question regarding a seasonality question found in the schweser study notes.
Can somebody explain the reasoning behind this problem. I understand how to detect the seasonality and I looked at similar problems from the CFAI book too, however i think we need to know the number of observations in order to perform the T-test. I don`t understand how can schweser solve this without knowing the number of observations?
I pasted in the whol problem below. All comments are apreciated.
Regression Results for monthly cash flow study
Coefficients Standard Error T-Statistic p-Value
Intercept 26.8625 12.15146 2.210639 0.035719
Lag 1 0.7196 0.042584 16.89837
Autocorrelation of the residual
Lag Autocorrelation Standard Error T-statistic p-Value
12 -0.0254 0.0632 -0.4019 0.5612
Question: Does the information above indicate the presence of seasonality?
A, No, because the lag 12 autocorrelation of the residual is not significant.
B, Yes, because the lag 12 autocorrelation of the residual is significantly different than one.
C, There is not enough information provided, the autocorrelation for the first lag is also needed
to detect seasonality.
The good answer was choice A.

kkn006

I really apreciate your answer.