Answer:
Michael and Bart did not finish their experiment in science class so Mr. Velasquez asked them to stop by after school. However, they couldn’t because they had football practice.
Step-by-step explanation:
According to the given sentence, "Michael and Bart did not finish their experiment in science class so Mr. Velasquez asked them to stop by after school however they couldn’t because they had football practice", some elements of the sentence are incorrect, such as punctuation, capitalization, etc.
Therefore, the sentence should BEST be written as "Michael and Bart did not finish their experiment in science class so Mr. Velasquez asked them to stop by after school. However, they couldn’t because they had football practice."
With the addition of period, the two differing ideas are separated which makes them have a better meaning.