Why have biologists hypothesized that the first land plants had a low, sprawling growth habit? (A) They were tied to the water for reproduction, thus needing to remain in close contact with the moist soil. (B) The ancestors of land plants, green algae, lacked the structural support to stand erect in air. (C) Land animals of that period were small and could not pollinate tall plants. (D) There was less competition for space, so they simply spread out flat.