remained short for several centuries, then became much taller over the last 50 years. have consistently grown taller over the last two centuries. vary in height primarily because of the degree of various stressors on each population. vary in height because of genetic differences between groups.

Vary in height primarily because of the degree of various stressors on each population

Explanation:

Shorter plants became taller because of the various stressors such as unavailability of sunlight. Due to unavailability of sunlight, the plants grow taller for gaining solar radiation that is required for the process of photosynthesis. So we can say that the environmental condition or stress brought changes in the plant body.  

Option A : the fern transitined from gametophyte generation to sporophyte generation.

Leslie argues that an organism called a Euglena is a plant because it is eukaryotic, has a nucleus, makes its own food, and is unicellular. Where is Leslie's error? Plants do not make their own food..

In school, Brendan has been conditioned to get up from his seat every time he hears the school bell ring.

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The Parker probe.

Explaination:

for six years an artificial fertilizer is used on a apple orchard the orchard is next to a stream which empties in to a slat water bay during the last 5 years researchers have observed an increase in algae in the bay they have also sampled fish populations in the bay each year apex...

Answer:

Effective food supply was most likely an effect on society that resulted from improvements in blood handling during World War I and World War II.

One parrot species that feeds on large seeds nests is in the same tree as a parakeet that feeds on small seeds, they occupy different niches.

Myths about aging : 

Depression and loneliness are normal in older adults. ...

The older I get, the less sleep I need. ...

Older adults can't learn new things. ...

It is inevitable that older people will get dementia. ...

Older adults should take it easy and avoid exercise so they don't get injured.

A spring is a natural discharge point of subterranean water at the surface of the ground or directly into the bed of a stream, lake, or sea. Water that emerges at the surface without a perceptible current is called a seep. Wells are holes excavated to bring water and other underground fluids to the surface.

The image shows a cross-section of land scape.