Which tissue type is responsible for propelling food along the digestive tract?

Smooth muscle is the type of muscle tissue responsible for propelling food along the digestive tract.

Smooth muscle is a type of muscle tissue that can be found in the walls of hollow organs of the body such as the digestive system, urinary tracts, tubes such as blood vessels and reproductive system. Smooth muscles contracts involuntarily and allows the walls of organs to move. The layer of smooth muscle present in the digestive system helps to break down food and propel it along the tract. Food substances and liquid moves from one organ to the next through the muscle action.

it would lead to upper respiratory infections and pneumonia.

the correct answer is: b. pantala flavescens, because these organisms would have a high level of genetic variation due to sexual reproduction.  

because involves two organisms (parents) whose genetic material combines, sexual reproduction leads to genetic variation in new generations of offspring. the offspring is an unique organism, with new genome, more protected with the higher ability to adapted. this process is fundamental to evolution.