Heterogeneous mixture
a. vinegar
b. air
c. chunky peanut butter

The best answer is C.A heterogeneous mixture consists of two or more materials that have been physically combined but are unevenly mixed and can easily be identified from each other.

 Chunky peanut butter is an uneven mix of peanuts and other food products.  Bits of peanuts can easily be identified from the rest of the butter.

Other examples are :

1. mixture of sand and iron filings.2. Mixture of gold and silver powder.3. Vegetable or fruit  salad.4. Mixture of sand and water.5. Mixture of oil and water.6. Mixture of sand and fine gravel

the answer is "a.) well–developed vascular system."

explanation:

c. is the correct answer