题目

    Short and shy, Ben Saunders was the last kid in his class picked for any sports team. Football，tennis, Cricket—anything with a round ball, I was useless. he says now with a laugh. But back then he was the object of jokes in school gym classes in England's rural Devonshire.     It was a mountain bike he received for his 15th birthday that changed him. At first the teen went biking alone in a nearby forest. Then he began to cycle along with a runner friend. Gradually, Saunders set his mind on building up his body, increasing his speed, strength and endurance. At age 18, he 下列说法正确的是（    ）A．电场是为了研究问题的方便而没想的一种物质，实际上不存在B．电荷所受的电场力越大，该点的电场强度一定越大C．以点电荷为球心，r为半径的球面上各点的场强都相同D．在电场中某点放入试探电荷q，该点的场强为E=F/q，取走q后，该点的场强不为零