What must differ between the atom of two different elements

Can someone me with this and tell me what’s fracking and what does it have to do with carbon, carbon dioxide, or fossil fuels?

What was dr. willem johan kolff’s first step in using the scientific process to invent the hemodialysis machine? he built the machine and tried it with various patients, collecting data about its effectiveness. when a patient’s kidneys failed, he wondered if it would be possible to perform kidney functions with an external machine. he researched and collected data about numerous patients who exhibited symptoms of kidney failure. he drew conclusions from studies of various symptoms of kidney failure, and drew a design for the ideal external blood-processing machine.

What are the possible blood types among the children of parents that are ab and ii? oa) types a and b ob) types a, b, and ab c) types a, b, and o od) types a, b, ab, and o