Final answer:
The transitional word that would best complete the sentence is 'However', which introduces a contrasting idea.
Step-by-step explanation:
The transitional word that would best complete the sentence is However.
The sentence is stating that the student went to the mall after school, but then there is a contrasting idea introduced with the conjunction. The word 'however' indicates a contradiction or opposing idea to what was previously mentioned. In this case, it shows that the student did not have much money to spend despite going to the mall.