Sliding filament theory can be best explained as:
Actin and Myosin filaments do not shorten but rather slide pass each other
When myofilaments slide pass each other, Myosin filaments shorten while Actin filaments do not shorten
When myofilaments slide pass each other Actin filaments shorten while Myosin filament do not shorten
Actin and Myosin filaments shorten and slide pass each other
Hence, the correct answer is option 1).