With age, muscles can become weaker. this is due to
a. connections between nerves, which cause more pain and therefore less use
b. damage from everyday use and injuries that accumulate over time
c. disconnections between motor nerves and muscle fibers
d. difficulties that occur during muscle growth and repair

The answer is letter C.

As we age the connection of our motor nerves to our muscle fibers tend to deteriorate. When this happens we tend to lose our balance and coordination as well as our overall muscular strength and endurance through time. This explains why we cannot perform some activities that we do when we were younger when we turn into adults. The brain is already having a hard time to recruit the necessary stimulus to be sent to the muscle fibers to perform necessary actions. This is why the human body is always compared to a ticking clock where any moment it could just give up because of its deteriorating nature. 

As long as it was one lick and the dog is a bigger dog, it should be fine. watch it carefully for a few days.

explanation:

two years ago, when picking flowers in the mountains back of yosemite valley, i found a book. it was blotted and storm-beaten; all of its outer pages were mealy and crumbly. the paper seemed to dissolve like the snow beneath which it had been buried, however; many of the inner pages were well preserved. and although all were more or less stained and torn, whole chapters were easily readable. this is the condition of the great open book of yosemite glaciers today; its granite pages have been torn and blurred by the same storms that wasted the castaway book.two years ago, when picking flowers in the mountains back of yosemite valley; i found a book. it was blotted and storm-beaten, all of its outer pages were mealy and crumbly. the paper seemed to dissolve like the snow beneath which it had been buried, however, many of the inner pages were well preserved. and although all were more or less stained and torn; whole chapters were easily readable. this is the condition of the great open book of yosemite glaciers today, its granite pages have been torn and blurred by the same storms that wasted the castaway book.