Could anyone helps me to check whether I use commas correctly in these sentences? Thank you!!! 1.I had chance to observe 10B6 class, consisting of 29 students. 2.The final scientist’s name, Maria Curie, was used to lead-in. 3.He used technique network and then, asked students. 4.He spoke slowly, repeated the instructions several times, and used mime or hand signals when students don’t understand