Hello!
Ions are charged particles, that explains why they have either a positive or negative charge. Since electrical signals contain charges, that also explains why they are often based on ions. Your answer would be D!
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- TetraFish
Hormones because if you think about it. Vertebrates must have backbones and mammals have them. And, humans are basically mammals. And the glands secrete hormones.
The vaccine was made in the past year, and the flu virus has mutated and grown resistant to this year's flu vaccine
