The alula is a small structure that is found on birds. It is located at the joint between the hand wing and the arm wings of birds and it is the freely moving, first digit of a bird's wing. It is normally used by birds in slow flight. In humans, the structure that is comparable to the alula is the thumb.
Antibiotics are ineffective against viruses because viruses do not have cells. Viruses are infectious agents that live within the cells of other living things. Antibiotics work by breaking down the cell walls of bacteria or interfering with the bacteria's ability to repair its cell's DNA, according to How Stuff Works.
You need three codons to make an amino acid.
Question 13 should be marine
Answer:
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail.
Explanation:
 a celestial object consisting of a nucleus of ice and dust and, when near the sun, a ‘tail’ of gas and dust particles pointing away from the sun.
