HIV, which only infects humans, is considered to have a host range, whereas rabies virus, which can infect a number of animals and humans, is considered to have a host range.

narrow, broad

Explanation:

Host range in epidemiology refers to the number of potential host species a pathogenic organism is capable of infecting provided all other conditions are met. A pathogen with several potential host is said to have a wide host range while the one with very few potential host is said to have a narrow host range.

Hence, HIV in this case is considered to have a narrow host range while rabies virus is considered to have a wide host range.

the element that provides strength to the exoskeletons of clams and oysters is phosphorus.

this is so because calcium carbonate is the main component in the shells. calcium carbonate is strengthened by phosphorus.

explanation:

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