$A$ renewable exhaustible natural resource is

If the circle $x^2+y^2=a^2$ intersects the hyperbola $xy=c^2$ in four points $(x_i, y_i)$,for $i=1, 2, 3, 4$,then $y_1+y_2+y_3+y_4$ equals

Order of toxicity among ammonia,urea and uric acid (from lower to higher) is

In the Davisson-Germer experiment, an electron beam of energy $75 \ eV$ falls normally on the surface of a crystal. If the maximum intensity is obtained at an angle of $45^{\circ}$ to the direction of the incident beam, then the inter-atomic distance in the lattice plane of the crystal will be :-............... $\mathring{A}$

In the circuit shown,the heat produced in $5 \Omega$ resistance due to current $I_2$ is $50 \text{ J/s}$. Then,the heat generated per second in $2 \Omega$ resistance is (in $\text{ J/s}$)

How many meiotic divisions are required to produce $100$ grains of wheat?