[size=13.4399995803833px]Which SAS program correctly reads the data in the raw data file that is referenced by the fileref Volunteer[size=13.4399995803833px]?

[size=13.4399995803833px]Raw Data File Volunteer

1---+----10---+----20---+----30

ARLENE BIGGERSTAFF 19 UNC 2

JOSEPH CONSTANTINO 21 CLEM 2

MARTIN FIELDS 18 UNCG 1

	a.	data perm.contest;   infile volunteer;    input FirstName $ LastName $ Age          School $ Class; run;
	b.	data perm.contest;     infile volunteer;     length LastName $ 11;     input FirstName $ lastname $ Age           School $ Class; run;
	c.	data perm.contest;     infile volunteer;     input FirstName $ lastname $ Age           School $ Class;     length LastName $ 11; run;
	d.	data perm.contest;     infile volunteer;     input FirstName $ LastName $ 11. Age           School $ Class; run;

为什么B对D不对呢？ 请大神帮忙解释一下。谢谢！