Correct Answer is Option (C)

Number of turns per meter $=7000$ turns per $\mathrm{m}$

$\begin{array}{rlr}& i=2\mathrm{A}& \\ \\ & B={\mu }_{0}ni=4\pi \times {10}^{-7}\times 7000\times 2\\ \\ & =56\pi \times {10}^{-4}\mathrm{T}\\ \\ & =56\times \frac{22}{7}\times {10}^{-4}\mathrm{T}\\ \\ & =176\times {10}^{-4}\mathrm{T}\end{array}$

Correct Answer is Option (D)

Inside a hollow cylindrical conductor with uniform current distribution net magnetic field is zero in hollow space.

But outside the cylindrical conductor $B\propto \frac{1}{r}$

$\Rightarrow$ Graph in option D would be a correct one

Correct Answer is Option (A)

$B={\mu }_{0}ni$

Now $i\to 2i$

And $n\to \frac{n}{2}$

$B^{\prime }={\mu }_0\frac{n}{2}\times 2i={\mu }_{0}ni=B$

Correct Answer is Option (B)

$\int \bar{B}.\overline{dl}={\mu }_0{I}_{in}$

$\Rightarrow B\times 2\pi r=\frac{{\mu }_{0}I}{\pi R^2}\times \pi r^2$

$\Rightarrow B\propto r$

Correct Answer is Option (C)

$B=\frac{{\mu }_{0}I}{2r}$

$B_a=\frac{{\mu }_{0}I{r}^2}{2\left(r^2+\frac{r^2}{4}\right)}$

$\Rightarrow \frac{B_a}{B}={\left(\frac{2}{\sqrt{5}}\right)}^3$

$\Rightarrow B_a={\left(\frac{2}{\sqrt{5}}\right)}^{3}B$