A taxpayer with 2017 AGI of $160,000 has no income tax withholding and is required to pay estimated taxes. The taxpayer can avoid an underpayment penalty by paying

a. At least 90% of the  2017 tax liability ratably over four quarterly payments.

b. At least 110% of the 2017 tax liability ratably over four quarterly payments.

c. At least 90% of the 2016 tax liability ratably over four quarterly payments.

d. 100% of the 2017 tax liability ratably over four quarterly payments.