Determine the number of subshells in the following: first shell, second shell, and third shell.

• A. The first, second, and third shells all contain one subshell.
• B. The first shell contains one subshell.
  The second shell contains two subshells.
  The third shell contains three subshells.
• C. The first shell contains two subshells.
  The second shell contains three subshells.
  The third shell contains four subshells.
• D. The first shell contains three subshells.
  The second shell contains two subshells.
  The third shell contains one subshell.