GMAT Sentence Correction (SC) | When ethnic groups intermarry, it is likely

chetan2u

B) The intermarriage of ethnic groups is likely to result in cognitive benefits and may indeed have contributed to the Flynn effect,

I selected (B) because of following understanding

1. 'Have Contributed' shows the effect as reflected by Present Perfect Tense. Was this the main point?
2. Also, The noun modifier after the comma.