Which of the following does not produce $NO_2$ gas with concentrated $HNO_3$?

Heterosis is . . . . . . .

There are two holes,one each along the opposite sides of a wide rectangular tank. The cross-section of each hole is $0.01 ~m^2$ and the vertical distance between the holes is $1 ~m$. The tank is filled with water. The net force on the tank in newtons when the water flows out of the holes is (Density of water $= 1000 ~kg/m^3$,$g = 10 ~m/s^2$):

The number of electrons in the valence shell of the central atom of a molecule is $8$. The molecule is

Two fair dice are rolled. The probability of the sum of digits on their faces being greater than or equal to $10$ is

Two dice are thrown simultaneously,the probability of obtaining a total score of $5$ is