Option E is the correct code snippet. It first sorts the data in ascending order of TotalPurchaseAmount using PROC SORT. Then, it uses a DATA step to create a new dataset called Top10Customers, selecting only the first 10 observations from the sorted dataset. This effectively retrieves the top 10 customers with the highest total purchase amount. Option A sorts in ascending order, not descending. Option B uses the wrong syntax for descending order (BY DESCENDING Option C is incorrect because NODIJPKEY removes duplicate observations, which may not be what is intended in this scenario. Option D uses the wrong syntax for descending order (BY - . DESCENDING).

The step that reads the SASHELP.BASEBALL data set and creates the temporary data set CATCHERS is:
data catchers;
set sashelp.baseball;
where position='C';
run;
This DATA step creates a new data set named catchers by reading in data from sashelp.baseball and selecting only those observations where the variable position has the value 'C', which stands for catchers.

Both the KEEP= and DROP= options can be used to select specific variables in a dataset Option A and B use the KEEP= and DROP= options within the SET statement, respectively to achieve the desired result. Option D also uses the DROP= option but outside the SET statement, which is an equally valid way to select specific variables- Option C is incorrect because the KEEP= option needs to be inside the SET statement when used with the DROP= option. Option E is incorrect as the KEEP= option requires variables to be separated by spaces, not commas, within the SET statement.

This LIBNAME statement correctly uses the SERVER option to specify the Unix server, the path '/home/datasets/CustomerData' for the dataset location, and the USER and PASSWORD options for authentication. The order of options can be flexible, but ifs best practice to put the path after the server and before the user and password options. Option A is incorrect because it doesnt have the correct path of the dataset and it is not the correct syntax. Option B is incorrect because it doesn't have the correct path of the dataset and it is not the correct syntax. Option C is incorrect because the server is not the first keyword specified in the statement and it is not the correct syntax. Option E is incorrect because it doesn't explicitly use the SERVER keyword and the correct path should be written in a specific format.

Option A uses a DATA step with a BY statement to identify and output the first occurrence of each unique city- Option B sorts the dataset by City and then uses a DATA step with a BY statement to output only the first occurrence of each city Option C uses PROC SQL's DISTINCT keyword to select only unique city names- Option D is incorrect because it outputs the last observation of each city Option E is incorrect because it creates a frequency table, not a dataset with unique city names.