So on this problem question:
For a sample size of 17, with a mean of 116.23 and a variance of 245.55, the width of a 90% confidence interval using the appropriate tdistribution is closest to:
So we simply know the DF is 16
What confuses me is:

If it isn’t specified as one tail or two tail, does the default is two tail?

If it’s two tail, do we check the " Level of significance for two tail table" at
a. check the value at 10% / 2 = 5% = 0.05 significance = 2.120
or
b. check the value at 10% = 0.1 significance = 1.746
 If it’s one tail, do we simply check the 10% value at one tail table?