To determine the number of observations in the temp dataset after executing the given SAS code, we need to understand the functionality of the SET statement and the effect of the FIRSTOBS option.
In the given code, the SET statement is used to read observations from the test dataset and store them in the temp dataset. The FIRSTOBS option is used to specify the starting observation number to read from the test dataset.
Since FIRSTOBS = 75 is specified in the SET statement, SAS will start reading observations from the test dataset starting from observation number 75.
Therefore, the number of observations in the temp dataset will be the total number of observations in the test dataset minus 74 (since we start reading from observation 75).
Given that the number of observations in the test dataset is 500, the number of observations in the temp dataset will be 500 - 74 = 426.
Therefore, the correct answer is D) 426.