Which of the following groups of cells in the male gonad represents haploid cells?

$A$ car is moving along a straight line,say $OP$ in the given figure. It moves from $O$ to $P$ in $18 \; s$ and returns from $P$ to $Q$ in $6.0 \; s$. What are the average velocity and average speed of the car in going from $O$ to $P$?

The de-Broglie wavelength of the electron in the ground state of the hydrogen atom is . . . . . . $\mathring{A}$ (radius of the first orbit of hydrogen atom $= 0.53 \ \mathring{A}$).

If $\frac{2 x^3+x^2-5}{x^4-25}=\frac{A x+B}{x^2-5}+\frac{C x+1}{x^2+5}$,then $(A, B, C)$ equals to

$y+x^2=\frac{dy}{dx}$ has the solution

Ammonia forms the complex $[Cu(NH_3)_4]^{2+}$ with copper ions in alkaline solution but not in acidic solution. The reason for this is