Which paragraph effectively utilizes a variety of sentence structures?

a) though these are all wonderful contributions, many urban farmers are looking at an even bigger picture. many people believe that the goal of urban agriculture is to create a sustainable food supply for the entire city. while this could take years and a lot of elbow grease, people are quickly realizing the benefits of city farming.

b) city gardens also promote community. many of the non-profit organizations that establish and manage city gardens enlist neighborhood volunteers to with weeding, watering, planting, and harvesting. a box of vegetables and the knowledge that they are their communities are the only rewards these volunteers seek.

c) urban agriculture has taken hold in many cities across canada and europe—the practice is still a novelty in many u. s. cities. organizers are hoping to change people’s ideas about farming by showing people that big things can happen with a little patch of soil and some seeds. recently, volunteers transformed the lawn in front of san francisco’s city hall from a quarter acre of grass into a lush garden of tomatoes, spinach, and beans. san francisco’s food bank will receive donations from the harvested food.

d) there are many other advantages to urban agriculture, including the comfort that comes from knowing exactly where your food came from. city gardens also tackle nutrition by providing citizens with access to fresh, affordable produce. there are economic advantages to building gardens in vacant lots or unused lawns. many city gardens supply food banks with much needed vegetables and fruit. others sell the crops for profit, with the money going back into city projects. guided tours of the garden can also add to students’ knowledge of the importance of agriculture and nutrition.