What does it mean to be a sad ?

Explanation:

To enter a stage of negativness

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See below:

Explanation:

Although this is a very varying question, scientifically, being sad is when a hormone called serotonin is altered. Being sad is not a good feeling. It is a feeling of being low, not in the mood for laughter and joy, and overall being irritable and unhappy. Often times people are sad for reasons that cause sadness, like the loss of a loved one or an argument with a friend.

the answer would be knowledge about cars!

what is shown in the image?

eukaryote

chloroplast

mitochondrion

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