Final answer:
Among the given expressions, (a) "0" and (b) "ab" + "cd" are of type String.
Step-by-step explanation:
The expressions (a) "0" and (b) "ab" + "cd" are of type String. In expression (a), the double quotes indicate that the value is a String literal. In expression (b), the concatenation of the two String literals 'ab' and 'cd' results in a String. On the other hand, expression (c) '0' is of type char because it is enclosed in single quotes. Therefore, the correct answer is (d) Both (a) and (b) above.