I need the answer to all of the qs

When describing down syndrome, it's important to note that a. it can be classified as a single-gene disorder b. it is caused when red blood cells cannot properly form hemoglobin c. it causes infected males to have low testosterone levels d. it is usually caused by three copies of chromosome 21 select the best answer from the choices provided. a b

What is the role of the ocular lens?

What are atoms of the same element with varying number of neutrons