21.   The college years, says University of Maryland senior Andrew Ashwal, are often when smoking becomes a lifelong habit.

a. + habit >>共 662
bad 9.92%
old 9.28%
eating 8.49%
spending 2.80%
smoking 2.23%
buying 2.16%
good 2.01%
drinking 1.91%
viewing 1.83%
driving 1.58%
lifelong 0.76%
lifelong + n. >>共 462
friend 7.43%
dream 5.31%
resident 4.39%
fan 3.26%
friendship 3.11%
interest 3.04%
passion 2.83%
love 2.26%
habit 1.49%
learning 1.34%
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