Final answer:
Infertility is the inability to conceive after trying to get pregnant for at least a year. It can be either primary or secondary. Around 10% of women aged 15 to 44 in the US have difficulty getting or staying pregnant. Therefore, the correct option is D
Step-by-step explanation:
Infertility is the inability of a sexually mature adult to reproduce by natural means. For scientific and medical purposes, infertility is generally defined as the failure to achieve a successful pregnancy after at least one year of regular, unprotected sexual intercourse. Infertility may be primary or secondary. Primary infertility applies cases in which an individual has never achieved a successful pregnancy. Secondary infertility applies to cases in which an individual has had at least one successful pregnancy, but fails to achieve another after trying for at least a year. Infertility is a common problem. About ten percent (6.1 million) of U.S. women aged 15 to 44 have difficulty getting or staying pregnant.