The correct answer is option 3 - Both I and II.

Statement I states that shale becomes slate through metamorphosis. This is correct because shale, which is a sedimentary rock composed of clay and silt, can undergo metamorphism, a process where it is subjected to heat and pressure, resulting in the formation of slate.

Statement II states that shale is converted to slate when it is subjected to tremendous pressure and high temperature. This is also correct because the process of metamorphism involves applying heat and pressure to shale, causing it to recrystallize and transform into slate.

Therefore, both statements I and II are correct. Shale does become slate through metamorphosis, which occurs when it is exposed to significant pressure and high temperatures.