When a satellite moves around the earth in a certain orbit,the quantity which remains constant is .........

$A$ large tank filled with water to a height $h$ is to be emptied through a small hole at the bottom. The ratio of the time taken for the level of water to fall from $h$ to $\frac{h}{2}$ and from $\frac{h}{2}$ to zero is:

The number of structural isomers for $C_6H_{14}$ is

Water is considered to be polluted if the dissolved oxygen $(D.O.)$ content is less than ... $ppm$ :

The input resistance of a common emitter transistor amplifier,if the output resistance is $500 \, k\Omega$,the current gain $\alpha = 0.98$ and power gain is $6.0625 \times 10^6$,is ......... $\Omega$.

Which of the following is a true characteristic of the Kingdom Plantae?