Beginning slowly in the 20s and 30s, and then more quickly after age , fluid intelligence decreases.

75

Explanation:

Fluid and Crystal intelligence can be regarded as a concept which was set up by Raymond Cattell, in the year 1963. He described this concept as the ability one has to perceive a particular relationships which is not connected to kind of instructions/ practice that is associated to that relationship. Fluid intelligence has to do with capability to think abstractly so that one can solve problems. It should be noted that as it Begins slowly in the 20s and 30s, and then more quickly after age 75, fluid intelligence decreases.

answer; the basal forebrain;

50% i think

explanation: