1. How does CO2 benefit forests? Why can too much CO2 be bad? Is Amazon releasing too much CO2? 2. Where is most of the CO2 coming from?
3. What's up with the Eastern part of the Amazon?
4. What's going on with the Western part of the Amazon?

step-by-step 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:

answer; (a) he was a u.s senator for 38 years;

are you asking for our opinion?