As earth travels in its different constellations are visible at different times of the year.
a.
atmosphere
c.
galaxy
b.
orbit
d.
star cluster

orbit

Explanation:

Our sky is divided into 88 areas known as constellations. These constellations are identified by the brightest stars of these areas forming a recognizable pattern. As the Earth travels in its orbit around the Sun, different constellations are visible at different times of the year. This is because different part of the sky is visible as earth goes around the Sun.

Thus, As Earth travels in its orbit different constellations are visible at different times of the year.

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i have found an answer to your question but use it as information.

information: because weak acids/bases have low concentration of hydrogen ions, the addition of water has a large impact on the ph. 2. a difference in 1 unit is a 10x difference in concentration for example; a liquid with ph of 3 is 10x more acidic than a liquid with a ph of 4. therefore, a liquid with a ph of 3 is stronger.

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