Which sentence contains faulty parallelism?
a. Soraya experienced the violence of war, the uncertainty of relocation, and the challenge of adapting to a new culture.
b. Running, cycling, and swimming all are activities that improve a person's cardiovascular health.
c. Recycling plastic, reusing items, and to use cloth grocery bags are three ways to reduce trash.
d. Without major reduction in the use of fossil fuels, global warming may become an unstoppable process on this planet.