Pls help and Thx!! What is considered an object's half-life?

Tall, cone-shaped mountains in which layers of lava alternate with layers of ash are called a. shield volcanoes. b. cinder cone volcanoes. c. composite volcanoes. d. lava plateaus. select the best answer from the choices provided a b c d i need asap

Atypical human cell is approximately 12.00 μm in diameter and enclosed by a membrane that is 5.000 nm thick. (a) what is the volume of the cell including the membrane? (b) what is the volume of the cell membrane? (c) what percent of the total volume does its membrane occupy? to simplify the calculations, model the cell as a sphere. enter your answers using four significant figures.

All individuals have two alleles for a given trait. according to mendel's these alleles are passed down one each from both mother and father.