If $f: R \rightarrow R$ and $g: R \rightarrow R$ are defined by $f(x)=2x+3$ and $g(x)=x^2+7$,then the values of $x$ such that $g(f(x))=8$ are

Two positively charged particles $m_{1}$ and $m_{2}$ have been accelerated across the same potential difference of $200 \ keV$ as shown below. Given mass of $m_{1} = 1 \ amu$ and $m_{2} = 4 \ amu$. The de Broglie wavelength of $m_{1}$ will be $x$ times that of $m_{2}$. The value of $x$ is . . . . . . . (nearest integer)

The more commonly used baking powder contains about $30 \% NaHCO_3, 20 \% NaAl(SO_4)_2, 10 \% Ca(H_2PO_4)_2$ and $40 \% $ starch. Which of the following statements is/are correct?

Which of the following is a method of plant tissue culture?

Which of the following allotropes of carbon is isomorphous with crystalline silicon?

Which one of the following reactions is an example of heterogeneous catalysis?