Which one of the following conditions, if true, could have ensured that male northern elephant seal dialects did not disappear?

• A. Besides Isla Guadalupe, there was one more surviving colony with the same average male call tempo from which no migration took place.
• B. The call tempo of individual immigrant male seals changed to match the average tempo of resident male seals in the host colony.
• C. Besides Isla Guadalupe, there was one more founder colony with the same average male call tempo from which male seals migrated to various other colonies.
• D. The call tempo of individual male seals in host colonies changed to match the average call tempo of immigrant male seals.