physiological research related to sexual orientation has focused the most on which of these characteristics?

I believe the answer is: Finger-length patterns

According to the statistic, men whose for finger is longer than their ring finger had higher tendencies to commit in a homosexual relationship compared to the  other type of hands. For women, homosexual tendencies tend to be prevalent among women whose ring finger is longer than the fore finger.

The changes to agriculture in the united states since 1900 is that increased mechanization has increased food production, thereby increasing the need for labor. there has been an increased need for higher speeds of food production due the fact that the population in the united states continues to rise.