$\begin{array}{ll}
\text{Noble Gas} & \text{Uses}\\
\text{1. Krypton} & \text{a. Filling incandescent bulbs } \\
\text{2. Argon} & \text{b. Airport Runway lighting and approach lights } \\
\text{3. Xenon} & \text{c. Heat transfer medium for nuclear reactions } \\
\text{4. Helium} & \text{d. Photographic flash tubes }
\end{array}$
$\begin{array}{1 1} 1 \rightarrow b, \; 2 \rightarrow a,\; 3 \rightarrow d,\; 4 \rightarrow c \\1 \rightarrow d, \; 2 \rightarrow c,\; 3 \rightarrow a,\; 4 \rightarrow b \\1 \rightarrow b, \; 2 \rightarrow a,\; 3 \rightarrow c,\; 4 \rightarrow d \\ 1 \rightarrow a, \; 2 \rightarrow b,\; 3 \rightarrow d,\; 4 \rightarrow c \end{array}$
