IELTS Cohesion & Coherence

Assignment: Which passage below is more cohesive, A or B? Why?
Leave your answer in the comments below.
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A. Without proper nutrition, students tend to have difficulty paying attention in school. They often fall behind academically because they cannot focus on classroom assignments.
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B. Without proper nutrition, students tend to have difficulty paying attention in school. Unless they can focus on classroom assignments, they often fall behind academically.

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