Now consider a single base mutation in a codon for leucine that creates a codon for phenylalanine. A true reversion changes the phenylalanine codon back to a codon for leucine. Which of the following leucine codon(s) could be mutated once to form a phenylalanine codon, and then mutated at a second site to restore a leucine codon?a. CUU
b. CUC
c. CUA
d. UUG
e. UUA
f. CUG

options A, B, D and E

Explanation:

leucine codons include: UUA, UUG, CUU, CUC, CUA, CUG

phenylalanine codons include: UUU, UUC.

CUU          

replace C with U to give

UUU phenylalanine codon

replace underlined with A

UUA leucine codon

CUC

replace underlined with U

UUC phenylalanine codon

replace underlined with A or G

UUA, UUG  leucine codons

UUG

replace underlined with U

UUU phenylalanine codons

replace underlined with C

CUU leucine codon

UUA

replace underlined with U or C

UUU or UUC phenylalanine codons

replace U with C

CUU or CUC leucine codons

increase soil erosion                                             reduce soil erosion

cattle grazing                                                         hydroseeding

deforestation                                                         contour plowing

                                                                                planting vegetation

plant roots basically hold the top soil

together and stop soil erosion because

in such situation top soil is not removed

during flood but cattle grazing causes

soil erosion because cattle consume the

grasses and herbs and top soil is exposed.

same situation occurs because of

deforestation, the trees and plants are cut

down to expose top soil which causes soil

erosion

i think that is new experiments yield untrustworthy data and should be carefully considered, because you don't know what will happen with the experiments.