What Is the Likely Connection Between the Metal Iridium and the Demise

question 181

Multiple Choice

What is the likely connection between the metal iridium and the demise of Earth's dinosaur population?

• A) Iridium, which is found in abundance on Earth's surface, is poisonous to reptiles.
• B) Iridium is found beneath Earth's crust. Meteor impacts during the dinosaur age probably exposed and uncovered enough of it to poison the dinosaurs.
• C) Iridium is found in meteorites but is rare on Earth. The existence of a worldwide layer of it suggests a large meteor impact during the dinosaur age. The impact probably raised enough dust to block out sunlight and kill the dinosaurs.
• D) Iridium is highly radioactive. Its presence in a geologic layer dating to the dinosaur age suggests that natural radioactivity reached dangerous levels at that time, and the dinosaurs died from overexposure.

---

Definitions:

Macula Lutea

A small, yellowish central area of the retina that is rich in cones and where visual acuity (sharpness) is highest.

Optic Disk

The point in the eye where the optic nerve enters the retina, often referred to as the blind spot since it lacks photoreceptors.

Negative Employment Message

Communication from an employer that conveys unfavorable job-related information, such as a rejection notice or a notice of termination.

Emotional Stake

The emotional investment or interest an individual has in the outcome of a situation or in another person.