54-year-old patient is diagnosed with a deep vein thrombosis, which puts him at an increased risk for developing pulmonary embolism. A decision is made to initiate treatment with an anticoagulant that has an immediate onset of effect and is not dependent on the depletion of vitamin K-dependent coagulation factors. The best choice for achieving this treatment goal is:

a. Enoxaparin

b. Warfarin

c. Aspirin

d. Abciximab