Match the following schedule of reinforcement with their description.
% Schedule and Descriptions
\begin{tabular}{|l|p{6cm}|}
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Schedule of Reinforcement & Description
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I. Fixed Ratio & (a) Reinforcement provided after an unpredictable number of responses.
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II. Fixed Interval & (b) Varying amount of time passes between two reinforcements.
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III. Variable Ratio & (c) Number of responses required for reinforcement is always the same.
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IV. Variable Interval & (d) The interval of time that must pass before reinforcement is always the same.
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\end{tabular}