Question: Which vegetable is used to make Arepas?
About the article "Arepa", section "Abstract".

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Harina PAN is used to make the maize flour dough also known as "masa de arepa" or "masarepa", which is used to make Venezuelan and Colombian dishes such as arepas, hallacas, or bollos.
Harina PAN is found in varieties made from white and yellow corn.
It contains no additives and is considered suitable for those with restricted diets. 
In Colombia and Venezuela, arepas may be made with tapioca flour rather than cornmeal.
Tapioca arepas probably predate cornmeal arepas; among traditional cultures of the Caribbean the name for them is casabe.
Throughout both Spanish and Portuguese South America, the tapioca, or yuca, starch is used to make regional variations of the baked cheese bun, known locally as "pandebono", "pan de yuca", "pão de queijo", "chipá", or "cuñapé", among other names.
The whole unprocessed cassava root also has a number of culinary uses throughout South America. 
A variant of the pupusa in El Salvador is the "pupusa de arroz".
Rice flour is used to make the dough and they are usually stuffed with chopped pork, cheese, beans, zucchini, and other vegetables.
They hail from the town of Olocuilta, located to the east of San Salvador, but are now readily available throughout the country.
Another regional variation, found in Alegría, is the "pupusa de banano", which calls for the addition of plantain bananas to the pupusa.
Pupusas made in the United States are typically made with Maseca (brand) commercial corn flour-masa mix) instead of fresh "masa harina".
Some high-end "pupuserías" in the United States use rice flour and wheat flour versions.
In Santa Fe, New Mexico, variations include using spinach, pepperoni, cheese, and green chile.
A similar Mexican dish is called a "gordita" (literally, "little fatty"), but "gorditas" are usually open at one end.
In Venezuela, they make "arepas" (where the dough is cooked first, and then sliced in half and stuffed somewhat like a hamburger).
Colombia has its own recipe of "arepas", but, unlike Venezuelan, Colombian "arepas" are usually eaten without filling, or the filling is placed inside the dough before cooking.
Pupusas are also found in neighboring Central American countries.
Honduran versions often use the local "quesillo" type of cheese for the filling.
In Costa Rica, the pupusa variant consists of two fried tortillas with white cheese between them.
Taco Cabana, a Tex-Mex chain in Texas, created a dish called the pupusa that has no relation to the Salvadorian food. 
Vegetable oils are also used to make biodiesel, which can be used like conventional diesel.
Some vegetable oil blends are used in unmodified vehicles but straight vegetable oil, also known as pure plant oil, needs specially prepared vehicles which have a method of heating the oil to reduce its viscosity.
The vegetable oil economy is growing and the availability of biodiesel around the world is increasing.
The NNFCC estimate that the total net greenhouse gas savings when using vegetable oils in place of fossil fuel-based alternatives for fuel production, range from 18 to 100%. 
The encenillo tree is used as source of tanning substances for the leather industry, giving to the leather a beautiful reddish color.
The wood is very appreciated in the timber industry and is used for cooking in the traditional preparation of the cheese arepas.