Consider the grammar rule $$E \to {E_1} - {E_2}$$ for arithmetic expressions. The code generated is targeted to a CPU having a single user register. The subtraction operation requires the first operand to be in the register. If E₁ and E₂ do not have any common sub-expression, in order to get the shortest possible code.

Match the followings:

Group-I

(a) Pointer data type
(b) Activation Record
(c) Repeat -Until
(d) Coercion

Group-II

(p) Type Conversion
(q) Dynamic Data Structure
(r) Recursion
(s) Nondeterministic loop