More than 4 million Americans take opioid prescription pain relievers for nonmedical uses. More than 400,000 Americans use heroin, a powerful opiate drug. Many people report misusing prescription opioids before starting to use heroin. Each year, more than 28,000 Americans die from opioid overdoses.
Normally a sperm can easily penetrate the egg, but if another sperm has already entered, or the sperm and/or egg is defective. Ignore the other answer because it merely restates your question. So a sperm can always penetrate an egg unless it is too late or either it or the egg is defected.
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A a challenge for medical institutions because of the number of people who need rapid access to it.
