Answer:
Light can travel in a vacuum, and its speed is constant even if the light source is moving.
Explanation:
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First of all, just to help you, here are examples of progressive verbs being used :
I
run every day.
I am
r</span>
unning today.
The action is the same for both, as are the nouns. The difference occurs in the tenses. The first sentence is in present tense and it shows the action is habitually happening each day. On the other hand, the second sentence indicates that the person is currently performing the action; the running is in progress. Therefore, this is the progressive tense.
To form the progressive tense, you need to add the correct form of to be in front of the -ing form of the verb. In the example above, 'am running' has am, a form of to be, and the -ing verb running. Progressive tense is important because it helps make the sequence of events clear and specific. Some actions are not simple; thus, you need to show the complexities of when and how events occur.
Hope this helped :)
