Despite reading numerous research studies that report the association of fast food consumption with heart disease and diabetes, Rachel continues to eat fast food and thinks that it is harmless. Rachel's thinking is an example of:

Belief perseverance

Explanation:

Belief perseverance can also be referred to as belief persistence; it is the tendency for an individual to hold to his/her own initial belief in something despite receiving a new information that debunks the basis of one's initial belief.  An individual prefers to discredit the new belief despite sufficient evidence to discredit one's initial belief, just because they misinterpret or totally see no significance on the new information that was received.

Rachael's thinking of fast foods of being harmless, despite the information that fast foods are harmful is called belief perseverance.

Belief perseverance also known as conceptual conservatism

Explanation:

Belief perseverance (also known as conceptual conservatism is

maintaining a belief despite new information that firmly contradicts

it. Such beliefs may even be strengthened when others attempt to

present evidence debunking them, a phenomenon known as the

backfire effect (compare boomerang effect). For example,

journalist Cari Romm, in a 2014 article in The Atlantic, describes a

study in which a group of people, concerned of the side effects of flu

shots, became less willing to receive them after being told that the

vaccination was entirely safe.

Since rationality involves conceptual flexibility, belief

perseverance is consistent with the view that human beings act at

times in an irrational manner. Philosopher F.C.S. Schiller holds that

belief perseverance "deserves to rank among the fundamental 'laws'

of nature".

i am going to guess that it is co2.