Here
for c , validation test is described as "process to make sure the product satisfies the specified requirements at the end of the development phase. In other words, to make sure the product is built as per customer requirements."
so for this (i) requirement option is more feasible.
for b , system test is described as "he testing to ensure that by putting the software in different environments (e.g., Operating Systems) it still works. System testing is done with full system implementation and environment"
so options (iv) system engineering is more feasible
now for a , unit test is best described as "testing of an individual unit or group of related units.t is often done by the programmer to test that the unit he/she has implemented is producing expected output against given input"
so for this option (iii) code is more feasible
at the end for d , Integration test is described as "testing in which a group of components are combined to produce output. Also, the interaction between software and hardware is tested in integration testing if software and hardware components have any relation."
so i think option (ii) design is more feasible.
so ans should be
a -> iii
b ->iv
c ->i
d -> ii
Please correct me if i am wrong.Hope it helps.