The navel is located in the region of the abdominopelvic cavity.

The abdominopelvic is composed of the abdominal cavity and the pelvic cavity. This cavity contains the organs such as liver, stomach, spleen, gallbladder, pancreas, kidney and most of the intestines along with the internal reproductive organs and urinary tract. The navel is located in the umbilical region of the abdominopelvic cavity.

Hence, the blank can be filled with 'umbilical region'.

the father in the first generation probably had the recessive colorblind trait in his x chromosome. if he and his wife both had the colorblind trait, even if she had 1 recessive and 1 dominant, then that trait would be passed on to their kids.

(since you didn't attach the family tree this is just an assumption)

correct answer is option a.

tropopause, stratopause and mesopause have all in common aspect that is point of maximum temperature in its layer of the atmosphere. all layers of atmosphere observe abrupt change in temperature. tropopause is the boundary between troposphere and stratosphere. stratopause is the boundary between stratosphere and mesosphere. mesopause is the boundary between mesosphere and thermosphere. these all boundaries are ranges between altitude of 0 to 80 km.