According to the sliding-filament model of muscle contraction, asarcomere contracts when its ______.
A) thick filaments slide across its Zlines
B) thick filaments slide toward eachother across its thin filaments
C) thin filaments slide across its Zlines
D) thick filaments shorten, pulling theopposed sets of thin filaments past each other
E) thin filaments slide toward each other across its thickfilaments