Love was in the air in a Tokyo park as normally staid Japanese husbands gathered to scream out their feelings for their wives, promising（）and extra tight hugs.

A. whether variations in intelligence are caused by genetic differences
B. how to overpower genetic factors with new educational approaches
C. whether genetic contribution to one’s intelligence varies with age
D. the relationship between environment and genes

A. genetic contribution increases when one grows older
B. genetic influence decreases when age increases
C. environment has more impact on fraternal twins than identical twins
D. it remains a mystery how genes and environment co-influence people