Which word does the underlined clause modify?

a biologist who studies marine animals is fascinated by this ecosystem.

a.
fascinated

b.
biologist

c.
ecosystem

d.
is

glamis thou art, and cawdor; and shalt be what thou art promis'd; yet do i fear thy nature; it is too full o' the milk of human kindness to catch the nearest way: thou wouldst be great; art not without ambition; but without the illness should attend it. what thou wouldst highly, that wouldst thou holily; wouldst not play false, and yet wouldst wrongly win: thou'dst have, great glamis, that which cries, "thus thou must do, if thou have it: and that which rather thou dost fear to do than wishest should be undone." hie thee hither, that i may pour my spirits in thine ear; and chastise with the valor of my tongue all that impedes thee from the golden round, which fate and metaphysical aid doth seem to have thee crown'd withal.  

he lacks ambition.  

he is hesitant.  

he lacks courage.  

he has moral scruples.

type of error:

the error in the sentence is a "dangling modifier". a dangling modifier is a phrase, word or clause that "dangles" because there is not target to modify. in this case, "after mopping the floor" is the dangling modifier since it has no word to modify. the noun "house" cannot mop the floor; therefore there is a mistake in the writing of the sentence.

showing or having an insensitive and cruel disregard for others. (so basically being heartless)

hope this : )

the development of trade during the middle age increased to the change given in the agriculture, which gave money, industry and markets a bigger importance in economy. the agriculture production was more than the consumption, which meant the creation of wider markets out of the areas. besides, with the end of multiple wars, the population increased and new trade routes were created.