Final answer:
The sentence should start with 'Based on' to accurately convey the information derived from scientific studies about the T-Rex's habitat and era. The T-Rex lived during the Cretaceous Period and faced extinction due to catastrophic events like an asteroid impact.
Step-by-step explanation:
The correct answer to the student's question is A. Based on. Using this phrase, the complete sentence reads "Based on scientific findings, we know that the T-Rex lived over 65 million years ago near river valleys in North America." This is supported by extensive research into dinosaur fossils and geochronology that has provided us with substantial evidence about the existence and timeline of the Tyrannosaurus Rex.
During the Cretaceous Period, which took place from 145 to 65 million years ago, dinosaurs like the T-Rex reached their peak in size and distribution. The T-Rex was an impressive predator, weighing at least 7 tons. The Cretaceous Period is also known for its warm climate and the dramatic extinction of the dinosaurs, attributed to events such as asteroid impacts and massive volcanic eruptions. These events led to environmental changes that were detrimental to the dinosaurs' survival, ultimately causing their extinction.
Furthermore, the impact of the asteroid that created the Chicxulub crater is another significant piece of evidence pointing to the extinction cause. It generated environmental disasters and large-scale volcanic eruptions that altered the Earth's climate and vegetation, making it a less hospitable place for dinosaurs.