The answer is 50%.
From the 'National Affairs' website, they conducted a study where they found that less than 20% of couples who married in 1950 ended up divorced, about 50% of couples who married in 1970 did.
And in regards to the basic unit of society question; the answer would be family. Family is the basic unit of society as it forms community and is the nucleus of civilisation.
B. Ensure hours of operation that are convenient to patients with limited English proficiency.
B; enlargement of the frontal lobe
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