You are studying a protein and notice that it contains two regions made of beta-sheets connected by an alpha-helix. This type of recurring structure that can be found in proteins with very different functions is called a:

Motif

Explanation:

Motif (super secondary structures) are similar three dimensional structure conserved in different proteins and perform the similar function. But we cannot predict the function of a protein from the presence of motif because there are several proteins and enzymes that have the same motif but perform different functions.

Structural motif in protein describe the interaction between secondary structures such as helix-turn-helix.

Example; Beta hairpin is an example of motif in which a strong turn of few amino acids connect the two strands

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.

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.