Which of the following reveals a pattern observed by scientists?
a. hot springs are warmed year-round by melted rock.
b. a woman can get pregnant at a certain time each month.
c. mud sometimes smells like rotten eggs because of chemicals
inside the mud
d. waves on the ocean can be very tall.

a patient chooses to not take a beneficial medical treatment.

explanation:

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6