The selection 2 in the given excerpt from 'Eclair Recipe' by Maria Parloa primarily functions to elucidate the strategy or process that is adopted to prepare the chocolate eclairs. Since the question asks the first step, the answer would be 'putting the half-pint of milk into the double boiler' as it is the introductory step in the filling number two. <u>This step is followed by various other steps like 'beating it with specific amounts of flour, sugar, egg, etc. to reach a light level. addition of salt etc</u>.' that eventually results in preparations of delicious chocolate eclairs which are loved and admired by people for its heavenly taste. Thus, <u>option D</u> is the correct answer.
