The human heart starts beating arounddays of embryonic development(. ) a) 22
b) 21
c) 23
d) 24

a) 22

Explanation:

Cardiogenesis which is the formation of the heart begins by day 21. The heart begins to form as paired tubes. By days 22 - 23 of embryonic development, the heart begins to beat. This represents the formation of the first vital organ of the body and it also causes the formation of left-right asymmetry of the body.

The days are counted from the day of the last menstrual period.

ans.

gregor john mendel is known for study of inheritance in pea plants. he used garden pea plant for his study, having alternative traits for various characters. he performed cross-breeding in pea plants to check how characters are transmitted between parents to offspring, such as cross between pure tall and pure dwarf plant. mendel studied the inheritance patterns in pea plants for various generations.

thus, the correct answer includes options and f).

thinking it would be d not too sure but i think it's right