Step 1: Understanding HDI.
- The Human Development Index (HDI) is a composite index measuring a country's achievements in health, education, and income.
Step 2: Identifying the top-ranking country.
- As per UNDP reports, Norway has consistently ranked among the top countries in HDI.
- Norway is located in Europe.
Step 3: Elimination of options.
- (A) Asia → No Asian country is at the very top, though countries like Singapore and Japan score high.
- (C) North America → USA and Canada are high but not at the top.
- (D) Australia → Australia also scores very high but not rank 1.
Thus, the correct continent is Europe.
\[
\boxed{\text{The country with the highest HDI (Norway) is in Europe.}}
\]