Conflicting Viewpoints on Dark Matter

In a recent academic journal, two physicists presented conflicting viewpoints on the phenomenon of dark matter. Physicist A suggests that dark matter constitutes about 27% of the universe's total mass-energy content and is crucial for explaining observed gravitational effects on galaxies and clusters. He supports this claim with evidence from galaxy rotation curves and gravitational lensing observations.

On the other hand, Physicist B contends that the existence of dark matter has not been conclusively proven and argues that alternative theories, such as Modified Newtonian Dynamics (MOND), can explain the same phenomena without the need for dark matter. He highlights the lack of direct detection of dark matter particles in laboratory experiments as a key point against its existence.

Considering these arguments, which option best reflects Physicist A's position on dark matter?