$A$ scientist $X$ demonstrated that the extract of infected plants of $Y$ could cause infection in healthy plants and called the fluid as "Contagium vivum fluidum". Identify $X$ and $Y$.

• A
  $W. M. Stanley$, Potato
• B
  $M. W. Beijerinck$, Tobacco
• C
  $D. J. Ivanowsky$, Cauliflower
• D
  Pasteur, Tomato