Question

effect means :
a phenomenon that is caused by some previous phenomenon
an agreement establishing an association between groups
an addition to the length of something
the state of something that has been unused and ignored

Explanation:

The word "effect" refers to a result or consequence. The first option "a phenomenon that is caused by some previous phenomenon" aligns with this meaning as it implies a cause - and - effect relationship. The second option is more about an "alliance" or "treaty" (related to "agreement establishing an association"), the third is about "extension" (related to "addition to length"), and the fourth is about "neglect" (related to "unused and ignored").

Answer:

a phenomenon that is caused by some previous phenomenon