GIVING BRAINLIEST Why is it difficult to create a vaccine for the flu? A. a failure to induce immune response

B. antigen shifting

C. a loss of immunity

D. antibody shifting

Explain what a zygote is. use the terms egg cell, sperm cell, and fertilization in your explanation.

Which genetic disorders, caused by an extra x chromosome (xxy), is characterized by a lack of testicular development in males, effeminate features, possible mental impairment, and a thin stature?

Where does the esophagus lead to in a frog?