The name of the structure labeled as A is 'myosin'. Moreover, the name of the structure labeled as B is 'actin'.
A sarcomere is the basic unit of muscle contraction. This unit is defined as the region between two Z-lines.
Band A is a central band composed of the thick filaments of myosin.
Moreover, the sarcomere also has two halves of a band known as I-band, which consists of thin filaments of actin.
Muscle contraction is caused by the interaction between actin and myosin protein filaments in the sarcomeres.
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Answer:

Explanation:
It is given that
B is the dominant allele which represents the black color
and b is the recessive allele which represents the white fur.
B being dominant will result into black color fur for genotype "Bb"
Given -
Frequency of black fur allele (p) is 
As per Hardy Weinberg's first law of equilibrium

Substituting the value of p in above equation, we get -

q represents the frequency for white fur allele
Frequency of white fur phenotype is

Frequency of homozygous black fur phenotype (BB) is

As per Hardy Weinberg's second law of equilibrium -

Combined frequency of homozygous and heterozygous black fur phenotype is

At neuromuscular junctions, a neurotransmitter called as acetylcholine if found. Botulinum toxin inhibits the transmission of acetylcholine at the synaptic junctions. Botulin toxin acts at presynaptic junctions and blocks the release of acetylcholine, leading to paralysis.