Which of the following is $NOT$ obtained when a mixture of methyl bromide and ethyl bromide is treated with sodium metal in the presence of dry ether?

The two surfaces of a biconvex lens have the same radii of curvature. This lens is made of glass with a refractive index of $1.5$ and has a focal length of $10 ~cm$ in air. The lens is cut into two equal halves along a plane perpendicular to its principal axis to yield two plano-convex lenses. The two pieces are glued such that the convex surfaces touch each other. If this combination lens is immersed in water (refractive index $=$ $4/3$),its focal length (in $cm$) is:

Match the following:
| Column $I$ | Column $II$ |
| :--- | :--- |
| $A$. Hooke's law | $1$. Tangential strain |
| $B$. Shearing strain | $2$. Temporary loss of elastic property |
| $C$. Bulk strain | $3$. Elastic limit |
| $D$. Elastic fatigue | $4$. $3$ times the linear strain |

When substance $A$ reacts with water,it produces a combustible gas $B$ and a solution of substance $C$ in water. When another substance $D$ reacts with solution $C$,it produces the same gas $B$ even when reacting with dilute sulfuric acid at room temperature. $A$ imparts a golden yellow color to the non-luminous flame of a Bunsen burner. What are $A$,$B$,$C$,and $D$ respectively?

Which region is considered the secondary center of origin for coffee production?

Which of the following statements is not true?