I don't understand why "is teaching" has to be the translation, and "teaches" is not accepted. They are both in the present. What is the correct Swahili verb conjugation for "teaches?"

Esther is teaching a science lesson, or Esther is teaching science. Either of these is correct in English, but not the stated correct answer.

Sayansi should not be capitalized in this sentence. "sayansi" would be better.

I wrote teaches and was corrected "is teaches"... Double report, of course.