Read the passage carefully and select the best answer to each question out of the given four alternatives. The Amazon basin has been inhabited for thousands of years, but European powers tried to claim the region much later. No serious effort was made to control this territory until the Portuguese built a fort near the mouth of the river at Belem in 1616 and later sent Pedro Teixeira up the river and back between 1637 and 1639. During the seventeenth and eighteenth centuries, Portuguese adventurers pushed further into the forest. According to the passage, in which year did the Portuguese build the fort near the mouth of the river at Belem?

Introduction / Context:
This question asks about a specific historical date mentioned in a passage on the Amazon basin and Portuguese expansion. The passage links the building of a fort at Belem with the first serious attempt to claim the territory. We need to pick the correct year that the fort was constructed, as stated in the text.

Given Data / Assumptions:

• The passage notes that no serious effort was made to claim the Amazon basin until the Portuguese built a fort near the mouth of the river at Belem.
• It explicitly states that this fort was built in 1616.
• Later dates in the passage, 1637 and 1639, relate to Pedro Teixeira's journey, not to the construction of the fort.
• The question asks only for the year of the fort's construction.

Concept / Approach:
The approach is to distinguish between multiple dates mentioned in the same sentence and connect each date to the correct event. Many comprehension questions intentionally place several years close together to test whether readers can match them with their respective events.

Step-by-Step Solution:
Step 1: Identify the sentence that discusses Belem and the Portuguese fort.Step 2: Note that the text says the Portuguese built a fort near the mouth of the river at Belem in 1616.Step 3: Observe that the dates 1637 and 1639 refer to the period in which Pedro Teixeira travelled up the river and back.Step 4: Select the year 1616 from the options as the correct answer.

Verification / Alternative check:
To verify, re read the portion describing chronological events: first the fort in 1616, then Pedro Teixeira's expedition in the late 1630s. The temporal sequence makes it impossible to confuse the construction date with the later journey dates. This confirms that the correct year for the fort is 1616.

Why Other Options Are Wrong:
Option A, 1541, refers to the earlier Spanish expedition led by Gonzalo Pizarro and involving Francisco de Orellana, not to the Portuguese fort.
Option B, 1637, and option D, 1639, belong to the time span of Pedro Teixeira's journey and therefore do not indicate the year the fort was built.

Common Pitfalls:
A frequent error is mixing up dates that appear close together in the text. Students might remember 1637 or 1639 as important dates and choose them for the fort simply because they sound familiar. A careful reader separates the dates by event: 1616 for the fort, late 1630s for the expedition.

Final Answer:
The passage clearly states that the Portuguese built their fort near the river mouth at Belem in the year 1616. Thus, the correct answer is 1616.