Read the sentence.
Carrying two full grocery bags, Petra raced out of the store to her car.
How do the words "Carrying two full grocery bags" function in this sentence?
a. as a gerund that is the sentence's subject
b. as a participial phrase modifying the subject, Petra
c. as a gerund phrase modifying the verb, raced
d. as a participle that modifies the infinitive to her car