Answer:
Substance
<u>Review</u>:
⇒ One of a class of substances that cannot be separated into simpler substances by chemical means.
<u>Compound</u>:
⇒ A pure substance composed of two or more elements who composition is constant.
All galaxies have a dense core of stars. Spiral galaxies, however, have arms that are often visible. There are two kinds of spiral galaxies: barred, where there appears to be a line running from arm to arm through the core, and <span>ordinary, where there is no bar. @Badbunnyhunny</span>
<span>d. subsistence strategy.</span>
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