What is predicted by the second law of thermodynamics?

The amount of usable energy that is available for doing work in a system is known as:

$A$ solution that resists changes in $pH$ is a/an

Bones of birds are:

Choose the correct option.
$x$ - More than $70$ percent of all the species recorded are animals.
$y$ - The number of algae species in the world is more than the combined total of the species of fishes,amphibians,reptiles,and mammals.
$z$ - India is one of the $15$ mega diversity countries of the world.

The most abundant element present in the plants is