The question asks which water bodies have significantly shrunk or dried up due to human activities.

Option 1 states "1 only", referring to the Aral Sea. This is correct as due to irrigation projects, the Aral Sea has indeed shrunk vastly. Massive irrigation projects introduced by the Soviet government caused the Sea to lose its water at an alarming rate, leading to its current state.

Option 2 suggests that both the Black Sea and Lake Baikal have shrunk due to human activities. However, while they both face ecological issues, neither has substantially dried up or shrunk.

Option 3 mentions "2 only," indicating only the Black Sea has shrunk. This is incorrect as stated before; the Black Sea has not significantly dried up or shrunk due to human activity.

Option 4 says "1 and 3", indicating the Aral Sea and Lake Baikal. While the Aral Sea has indeed shrunk, Lake Baikal, the world`s deepest and oldest freshwater lake, has not substantially dried or shrunk.

Therefore, the correct answer is 1 – only the Aral Sea has shrunk immensely due to human activities.