52pickup is not a legal identifier. The first character of an identifier cannot be a digit.
In Java, the identifiers delete, thrown, exit, unsigned, and next are not keywords. Java has a goto keyword, but it is reserved and not currently used.
It is a completely valid comment. Comments do not nest. Everything from the start marker of a comment block (/*) until the first occurrence of the end marker of the comment block (*/) is ignored by the compiler.
(a) and (d)
String is a class, and "hello" and "t" denote String objects. Java only has the following primitive data types: boolean, byte, short, char, int, long, float, and double.
(a), (c), and (e)
Type (a) is a boolean data type, while types ...