Which cues might cause a plant to respond? clouds covering the sun

sunlight on the other side of a fence

the touch of a horse's tail

all of the above

sunlight on the other side of a fence

Explanation: The phenomena to exhibit a response is called Phototropism. Plants like other autothrops manufacture their own food through the process of photosynthesis, to do this, they need  to water, carbon dioxide, and minerals in the presence of sunlight. Phototropism occurs when plants grow towards  a source of light.

Therefore sunlight on the other side of a fence  is the only cue from the options that can make a plant to respond.

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