21.   Though details vary from state to state, the plans allow parents to pay in advance for college and shield them from rising tuition costs.

n. + vary >>共 929
price 6.22%
rate 3.25%
opinion 2.15%
estimate 1.96%
cost 1.84%
result 1.75%
time 1.59%
number 1.53%
rule 1.47%
fee 1.47%
detail 0.64%
detail + v. >>共 266
be 64.38%
remain 5.19%
have 4.54%
emerge 3.84%
need 1.24%
come 1.02%
add 0.99%
become 0.62%
include 0.59%
vary 0.59%
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