First person to answer this question gets brainliest a thanks and 5 stars!
A membrane that only "lets" certain molecules in while keeping other molecules out is ___ ___.
A) Flexible
B)Bilipid layers
C) Endoplasmic Reticulum (ER)

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.

weathering - colorado river carves land in arizona to form the grand canyon. cracks form in a sandstone wall surrounding a house. a marble statue near the science museum is changing color due to rainfall

erosion - after a rainstorm, soil and rock piees litter the roadways. the sand dunes in the sahara desert are changing shape.

here's your answer.