can anyone check if I'm right or wrong plz?

Question

A. Sedimentary formations may be in contact with other sedimentary formations, but not with igneous rocks. TRUE?

B. Two half-lives equals a whole life in radioactive decay. TRUE?

C. A given rock may contain more than one type of radioactive element, permitting independent age estimates to be obtained. TRUE?

D. A formation containing a particular set of index fossils is assumed by geologists to be the same age as any other formation containing the same set of index fossils. FALSE?

E. The rate of radioactive decay of a given element varies with changes in Earth's gravity and magnetic fields. TRUE?

-THANKS

Answer 1

A. True. Igneous rocks can have sediments resting on top of them, making an erosional contact. Also, igneous rocks can intrude into sedimentary rocks. When this happens there is generally contact metamorphism, but if the igneous rock temperature is low enough the sedimentary rocks might remain sedimentary rocks.
B. False. Two half lives equal two half lives. For carbon, a half life is about 5700 years. Two half lives is 11400 years. At this time 1/4 (1/2*1/2=1/4) of the original C14 remains.
C. True. Rocks could (for example) contain both uranium and thorium.
D. True. Index fossils are widespread (worldwide) and lived a short time geologically speaking.
E. False. Radioactive decay is due to the Weak Internucleic force, magnetism is the electro-magnetic force and gravity is the gravitational force. They have nothing to do with each other.

Answer 2

A. False: Sedimentary rocks can be resting over igneous basement or igneous bodies could be intrusive in sedimentary rocks.
B. False: Two half lives would be closer to a quarter life Half and then again half, so theoretically a full life deacy never happens.
C. True
D. True
E. False: These are independent phenomenoa.

Answer 3

you are 100 percent right