The greenhouse effect is related to

Vitamin $B_6$ is known as

An aeroplane flying with uniform speed horizontally $1 \ km$ above the ground is observed at an elevation of $60^{\circ}$. After $10 \ s$,if the elevation is observed to be $30^{\circ}$,then the speed of the plane (in $km/h$) is

In any $\triangle ABC$,$a(b \cos C - c \cos B)$ equals

Which group of organisms was the first to exist on Earth among the given options?

Compared to blood,our lymph has: