Final answer:
Recent decades in the U.S. have seen a dramatic increase in the popularity of Christian sects, with evangelical denominations growing significantly, exemplified by the Southern Baptist denomination which has become the largest. The correct answer is option: a. Christian sects.
Step-by-step explanation:
In the United States, the religious organizations that have seen a dramatic increase in popularity in recent decades are Christian sects. Notably, evangelical Christian denominations have experienced a significant surge in membership, with Southern Baptists becoming the nation's largest denomination.
Other Christian groups whose membership critically shapes one's daily life, like the Church of Jesus Christ of Latter-Day Saints, Seventh-Day Adventists, and the Assembly of God, have also seen tremendous growth and influence. These changes reflect broader shifts in religious affiliation and the dynamic nature of religious organization and influence in society.