Step 1: Note the nature of the \(-OH\) group.
In phenol the \(-OH\) group is an activating, ortho and para directing group. So electrophilic substitution like nitration takes place mainly at the ortho and para positions.
Step 2: Note the strength of the reagent.
Here the reagent is dilute \(HNO_3\) used at low temperature. This is a mild condition, so only a single nitro group is introduced (mononitration), not multiple.
Step 3: Decide the products.
Because the substitution is mild and \(-OH\) directs ortho and para, we get a mixture of o-nitrophenol and p-nitrophenol.
Step 4: Rule out the wrong choices.
2,4,6-trinitrophenol (picric acid) needs concentrated \(HNO_3\), not dilute, so that is wrong. Getting only ortho or only para is not correct because both positions react.
Step 5: Conclude.
Dilute \(HNO_3\) at low temperature gives a mixture of ortho- and para-nitrophenol.
\[ \boxed{\text{ortho- and para-nitrophenol}} \]