Amass extinction is defined as
a loss of 95 percent of species
an asteroid impact
a boundary between geological periods
a loss of 50 percent of species

95% of species

Explanation:

the word mass, means very large and widespread.

advantage of using stem cells in medical research:

1.       it provides medical benefits in the fields of therapeutic cloning and regenerative medicine.

2. it provides great potential for discovering treatments and cures to a variety of diseases including parkinson disease, spinal cord injuries, diabetes, alzheimer’s disease and many more.

3. limbs and organ could be grown in lab from stem cells and then used in transplant or treat illness.