The first one. Think of it as this. Take out the phrase the brakets are around and no one know what you're writing about. When you put the brakets in the setence with the terms you are telling the audience what "it" is
Answer:
I cannot write your essay for you but I can give you ideas.
Explanation:
If mass students are late, the most plausible cause is traffic and/or reliability problems with a ride. Recommendations for that could be expanding where buses pick up and drop off or adding another bus or if the streets are busy that time of day, changing the start time can also be an option.
Another reason could be too much homework clashing with getting up too early.