Density can be useful in identifying substances. It is also a convenient property because it provides a link (or conversion factor) between the mass and the volume of a substance. Mass and volume are extensive (or extrinsic) properties of matter - they depend on amount.
Scientists prove their hypothesis is true about Scientists can never "prove" their hypotheses are true, because some future experiment, possibly using new technology not currently available, might show the hypothesis to be false after all.
Answer: People were probably not getting vaccinated or the bacteria became immune to the vaccine.
Explanation: yw plz mark brainliest i need one more (:
