The Portuguese wanted to explore in the 1400s for several reasons, including:
- They wanted to expand trade.
- They wanted to expand Christianity.
- They wanted to reclaim trade routes.
While all the options reflect various motivations for exploration, the primary goals were to expand trade, establish new trade routes, and spread Christianity through exploration and colonization. Therefore, if you can only select one response, "They wanted to expand trade." is a key reason.