The question "How many people are in Twice?" requires clarification. "Twice" could refer to two things:
1. The South Korean Pop Group TWICE: This is the most likely interpretation. TWICE is a hugely popular K-Pop group, and the number of members has remained consistent since 2017. There are nine members in TWICE.
2. A metaphorical "twice": If "twice" refers to doubling a quantity of people, the answer depends entirely on the initial number. For example, "twice five people" equals ten people. The question needs to specify the original number of people to be doubled.
Therefore, the most accurate answer, given the typical interpretation, is nine.
