1. From which period is a rock at +2.7 m depth? A. Paleogene
B. Cretaceous

2. What is the average iridium content of rock 0.5 m below the K–Pg boundary layer?

A. 0.25 ppb
B. 0.30 ppb
C. 0.36 ppb
D. 41.6 ppb

3. How much more iridium was found in the K–Pg boundary layer than in rock 0.5 m below it?

A. 41.35 ppb
B. 41.60 ppb
C. 41.24 ppb
D. 39.62 ppb

The diagram shows the results when two parents are crossed. the letters represent alleles for a trait that is controlled by three different genes. which best describes this inheritance pattern? multiple allele because a trait is controlled by three different genes polygenic because the offspring have alleles from both parents multiple allele because the offspring have alleles from both parents polygenic because a trait is controlled by three different genes