Sentence Correction

Visitors to the park have often looked up into the leafy canopy and saw monkeys sleeping on the branches, whose arms and legs hang like socks on a chlothesline.

a, b and c wrong for starting with the same "saw".
d. Seen monkeys leeping on the branches, with arms and legs hanging

D is the correct and answer but I want to make sure of one tiny detail. in the original sentence you see the word LOOKED and therefore past tense but SEEN because it is perfect past. IS this reasoning correct. ALso my ear told me to choose seen. any comments people?

The cameras of the voyager II spacecraft detected six small, previously unseen moons circling uranus,which doubles to 12 the number of satellites now known as orbiting



a. same
b. doubling to 12 the number f satellites now know to orbit
c. which doubles to 12 the number of satellites now know in orbit around
d. doubling to 12 the number f satellites now know as orbiting
e. whichn doubles to 12 the number of satellites now known that orbit

since which has a non-essential non restrictive element to meaning. I eliminated a,c and E. THis leaves me with B and D and "known as orbiting" is unidiomatic. DO my thoughts on which qualify me to delete choice a c and E?