What does this excerpt tell you about the nature of the fighting in Vietnam?

The communist forces lacked heavy weapons like artillery.

American troops withdrew easily by helicopter.

US troops had to move and fight the enemy on the ground.

Fighting stopped during the night so each side could recover.

US troops had to move and fight the enemy on the ground.

Explanation:

american troops were forced to withdraw following deadly bombings.

explanation:

option d is correct. corroborated sources of historical evidence   is necessary to validate a claim about an event in history.

historians tend to use written sources, but audio and visual materials as well as artifacts are important objects that supply information to modern historians.

historical sources are usually divided into two categories: primary and secondary sources. depending on the historian's intent, some sources shift their designation. determining what type of sources toimplement, and the level of credibility and reliability of those sources, is a significant step in critical thinking for the historian.

explanation: