Read the following text to answer question.

Read the following text to answer question.

The nature of intelligence

For many years, scientists (1) ___________ define the nature of human intelligence. However, they (2) ___________unable to agree on whether there is one kind of intelligence, or several kinds. In the early 20th century, psychologist Charles Spearman came up with the concept of 'g' or 'general intelligence'. He (3) ___________ subjects a variety of different tests and (4) ___________ that the people who performed well in the tests used one part of the brain, which he called 'g', for all the tests. More recently, research (5)___________ that this idea may well be true, as one part of the brain (the lateral prefrontal cortex) shows increased blood flow during testing. However, some scientists believe that intelligence is a matter of how much people (6) ___________rather than some ability they are born with. They believe that environment also matters.

VINCE, M. Macmillan English grammar in context. Macmillan, London. 2008. p. 22. Adapted.

Check the alternative that shows the sequence of words that CORRECTLY fill in the spaces (1-6).