Let $\mathbf { r } = x \mathbf { i } + y \mathbf { j } + z \mathbf { k } \text { and } r = | \mathbf { r } | \text {. }$

question 17

Multiple Choice

Let $\mathbf { r } = x \mathbf { i } + y \mathbf { j } + z \mathbf { k } \text { and } r = | \mathbf { r } | \text {. }$ $\text { Find } \nabla \cdot ( 9 \mathbf { r } )$

• A) 9
• B) 45
• C) 18
• D) 27
• E) None of these

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Definitions:

Habitat Isolation

A type of prezygotic barrier where two species that could interbreed do not, because they inhabit different habitats and rarely encounter each other.

Environmental Isolation

The separation of population groups by physical barriers or distances, leading to genetic divergence and potentially speciation.

Biological Isolation

The separation of populations of the same species or different species that prevents genetic exchange, often leading to speciation.

Temporal Isolation

A mechanism that prevents species from mating because they breed at different times, contributing to reproductive isolation and speciation.