句子分析：新概念英语4中第47课多项选择题第一题答案是Themainreasonpeopleenjoycampingis,选cThemainreasonpeopleenjoycampingisnotnecessarilysothattheyaresavingmoney.这句话is后面看不大懂,特别是necess

　　句子分析：新概念英语4中第47课多项选择题第一题答案是Themainreasonpeopleenjoycampingis,选c

　　Themainreasonpeopleenjoycampingisnotnecessarilysothattheyaresavingmoney.这句话is后面看不大懂,特别是necessarily修饰哪个词,sothat这里又怎么解释?