Step 1: Understanding Unsaturated Hydrocarbons
Unsaturated hydrocarbons are those that contain one or more double or triple bonds between carbon atoms. The most common unsaturated hydrocarbons are alkenes and alkynes.
Step 2: Explanation of Other Options
- (A) CH\(_4\) is methane, which is a saturated hydrocarbon (alkane).
- (C) C\(_3\)H\(_8\) is propane, another saturated hydrocarbon (alkane).
- (D) C\(_4\)H\(_{10}\) is butane, a saturated hydrocarbon (alkane).
Thus, the correct answer is (B) C\(_2\)H\(_4\), which is ethene, an unsaturated hydrocarbon.

The correct structures of A and B formed in the following reactions are : 
The major product formed in the following reaction is : 
The following table shows the ages of the patients admitted in a hospital during a year. Find the mode and the median of these data.
\[\begin{array}{|c|c|c|c|c|c|c|} \hline Age (in years) & 5-15 & 15-25 & 25-35 & 35-45 & 45-55 & 55-65 \\ \hline \text{Number of patients} & \text{6} & \text{11} & \text{21} & \text{23} & \text{14} & \text{5} \\ \hline \end{array}\]