The layer of the uterus which becomes much eroded due to placental villi is known as

If $x$ and $y$ are acute angles such that $\cos x + \cos y = \frac{3}{2}$ and $\sin x + \sin y = \frac{3}{4}$,then $\sin(x+y)$ is equal to

$A$ bi-convex lens is formed with two thin plano-convex lenses as shown in the figure. The refractive index of the first lens is $1.5$ and that of the second lens is $1.2$. Both the curved surfaces have the same radius of curvature $R = 14\; cm$. For this bi-convex lens,if the object distance is $40\; cm$,the image distance will be: (in $; cm$)

When current in a coil changes from $5\,A$ to $2\,A$ in $0.1\,s$,an average voltage of $50\,V$ is produced. The self-inductance of the coil is $............H$.

How many nodal tissues (specialized cardiac musculature) are present in the human heart?

Which of the following compounds does not react with $NaNO_2$ and $HCl$?