Combine the following sentences using a subordinate conjunction.
esther observed the joyous look in josh's eyes. she whirled around to look up the hill.
a. esther observed the joyous look in josh's eyes, and she whirled around to look up the hill.
b. esther observed the joyous look in josh's eyes; she whirled around to look up the hill.
c. when esther observed the joyous look in josh's eyes, she whirled around to look up the hill.