PLZ HELP QUICK


Select all the correct answers. What is 221,000,000,000,000,000,000 expressed in scientific notation?

2.21 × 10^21

2.21E20

2.21E21

2.21E-20

2.21 × 10^-21

2.21 × 10^-20

2.21 × 10^20

2.21E-21