<span>The answer is Due to heating of the air by the engine exhaust. Contrails are formed when the hot exhaust of the plane engines is rapidly cooled by the cold air in the upper atmosphere. The water vapor in the engine exhaust, formed in the combustion of fuel, freezes immediately to ice crystals due to the low pressure and -36oC temperatures in the 8000 m altitude in which the planes cruise. </span>
A) A metal forms a + charged ion, so D2+
B) A nonmetal forms a - charged ion, so A-
C) C2-
D) B+
Biosphere. Bio means life, and Biosphere means ALL life on earth.
Answer:

Explanation:
Given -
Total Population - 
Individuals with homozygous HbA/hbA genotype - 
Individuals with homozygous hbs/hbs genotype -
Individuals with heterozygous hba/hbs genotype - 
Let us assume the given population is in Hardy Weinberg' equilibrium
The frequency of individuals in the given population with homozygous HbA/hba genotype is equal to number of individuals with homozygous HbA/hba genotype divided by total population.

The frequency of hba allele is equal to

Hummingbirds can fly as fast as 60 miles per hour. One reason why its a scientific question is because of their speed. Their speed is very different compared to many other animals. I hope this helps :)