The structure of $X$ is

$A$ body is projected vertically from the surface of the earth of radius $R$ with a velocity equal to half of the escape velocity. The maximum height reached by the body is

On addition of $1 \, mL$ of $10 \% \, NaCl$ solution to $10 \, mL$ gold sol in the presence of $0.25 \, g$ of starch,the coagulation is just prevented. The gold number of starch is:

If $A, B$,and $C$ are three sets,then $A - (B \cup C)$ is equal to

The equations of the tangents to the circle $x^2 + y^2 = 13$ at the points whose abscissa is $2$,are

Archegonia and antheridia in homosporous pteridophytes are present in: