Question marks - Prefix puzzle

2. Can mean happening twice a week OR happening once every two weeks.
4. A flat geometric shape with three straight sides and three angles.
6. A four-sided open area or courtyard enclosed by buildings.
9. One of four equal parts of a circle, coordinate plane, or map.
10. A chemical compound containing two carbonate groups or a salt containing hydrogen carbonate (like baking soda).
12. A very large number, equal to one thousand trillion.
13. Four children or offspring born at the same birth.
15. A 200th anniversary or the celebration of 200 years.
17. Happening once every two years.

1. Can mean happening twice a month OR happening once every two months.
3. Able to speak two languages fluently.
5. Happening twice a year (semi-annually).
7. An optical device with two lenses (one for each eye) used to see things far away clearly.
8. An all-terrain vehicle with four wheels.
11. A vehicle with three wheels moved by foot pedals.
13. To multiply by four, or an amount that is four times as large.
14. A large muscle on the back of the upper arm with three heads or points of origin.
16. A portable three-legged frame or stand used to hold a camera or other equipment steady.