Cytological examination of resting and contracted muscle provides important support for the sliding filaments model for how skeletal muscle contracts. this evidence includes the observation that during contraction the

The correct answer is that the H zone becomes narrower.

The H-band refers to the region of the thick filaments, which is not overlaid by the actin (thin filaments). Within the H-zone is a thin M-line, which is formed of cross-connecting components of the cytoskeleton.

At the time of muscle contraction, the A-bands do not vary in their length, whereas the H-zone and the I-bands shorten. This makes the Z-lines come near to each other.

the correct answer is - d. china has a large and growing population.

the fact that china has a large (the biggest) population, and it is still growing, doesn't hinder the agriculture production in the country. in fact, it can for increased production in the agriculture, since there's more labor force, as well the sheer mass of people produces lots of scientists that come up with new inventions as to how to improve this sector. nice example is the inner mongolia region in china, in general dominated by the gobi desert, but few scientist came up with a nice idea as to how to make the region productive by using plants that are very resistant to droughts, so lots of people have been employed, and the region is becoming greener and greener each year, and the production of food in this region is also increasing.