Two soap bubbles of radius 2 cm and 4 cm, respectively, are in contact with each other. The radius of curvature of the common surface, in cm, is _______________.
In an oscillating spring mass system, a spring is connected to a box filled with sand. As the box oscillates, sand leaks slowly out of the box vertically so that the average frequency ω(t) and average amplitude A(t) of the system change with time t. Which one of the following options schematically depicts these changes correctly? 
| List I | List II |
|---|---|
| A. Adenosine | III. Nucleoside |
| B. Adenylic acid | II. Nucleotide |
| C. Adenine | I. Nitrogen base |
| D. Alanine | IV. Amino acid |
Among the following, choose the ones with an equal number of atoms.
Choose the correct answer from the options given below: