10. While the kids ____________ in the garden, their mother came.

A. were playing        B. play                        C. is playing                 D. played

11. If you explained it to him more slowly, he ____________ it.

A. understands        B. would understand         C. understood                 D. will understand

12. People are now interested in saving money and ____________ resources.

A. natural                 B. naturalize                 C. nature                 D. naturally

13. Laura prepared for her exam ____________, so she passed it.

A. careless                 B. careful                 C. carefully                 D. care