Consider the following statements $A$ and $B$ and identify the correct answer:
$A$. Fresnel's diffraction pattern occurs when the source of light or the screen on which the diffraction pattern is seen,or when both,are at a finite distance from the aperture.
$B$. Diffracted light can be used to estimate the helical structure of nucleic acids.

• A
  $A$ and $B$ are true
• B
  $A$ and $B$ are false
• C
  $A$ is true but $B$ is false
• D
  $A$ is false but $B$ is true