I am no expert but in my opinion:
"that" serves to signal clarification. The subject the robot is being defined more specifically in the second part of the sentence and "that" is used as the signal to let the reader know that the first part connects to the second part of the sentence. "Performs" in this context would be that the robot goes through functions that result in phototaxis.
Hope this helps!
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October 27, 2011
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Corrected
My Job
Presently,I'm a new in the area of international trade. I'm earnest in my work,and I am ethusiastic about learning the technical skills of import and export. I have joined two international trade exchange groups,there are many expereience people in the group.Now they have become my mentors and friends.
