5. When muscles are exercised extensively in the absence of sufficient oxygen,
A. NADH molecules split
B. Lactic acid is produced
C. Cellular respiration ceases
D. A large amount of ATP is formed

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.

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.

ya the other dude is right

the correct answer is 2 and 4