How are animals divided into groups based on the morphological trait of the number of tissue layers during development?

a.) two groups: those that have three tissue layers in their embryos and those that have two

b.) three groups: those that have four, three, or two tissue layers in their embryos

c.) three groups: those that have three, two, or one tissue layers in their embryos

d.) two groups: those that have two tissue layers in their embryos and those that have one

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Explanation:

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.

colors do exist. the color of the sky is actually violet; humans percieve the color of the sky as blue.