In order for a physical barrier to be effective in preventing infection, the barrier must . A. prevent the substance from entering the body, trap the substance when it first enters the body, or flush the substance out of the body B. destroy the substance before it enters the body, prevent the substance from reproducing, or flush the substance out of the body C. trap the substance in t

a

Explanation:

1. loamy sand is about 80% sand with 10% clay and defined mostly by sand particles with some clay to provide structure and fertility. the sand particles are easily visible and the soil holds structure but breaks apart easily.

2. scott sand can improve his soil quality by incorporating more silt and organic matter into the soil. peat moss and organic matter can also be incorporated.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".