In humans, mammary gland is divided into lobes. | Agrigyan

Since all human ova carry an X chromosome, the sex of the zygote is determined entirely by whether the fertilizing sperm carries an X chromosome (yielding a girl, $XX$) or a Y chromosome (yielding a boy, $XY$).

The chronological sequence of female gametogenesis is:

• Oogonia (B) divide mitotically in the fetus.
• Primary oocytes (C) enter meiosis-I and arrest at prophase-I.
• Secondary oocytes (D) form at ovulation following completion of meiosis-I.
• Mature Ovum (A) forms upon fertilisation by sperm.

Mendel studied flower colour as Violet vs White (not pink vs white). All other listed pairs (inflated/constricted pods, axial/terminal flowers, green/yellow pods) were part of the 7 contrasting traits studied by Mendel in garden pea.