To match the works with their authors:
A. 'The Idylls of the King' is by III. Alfred Tennyson.
B. 'Dramatic Lyrics' is by II. A.C. Swinburne.
C. 'Sonnets from the Portuguese' is by I. Elizabeth Barrett Browning.
D. 'Poems and Ballads' is by IV. Robert Browning.
Thus, the correct matches are A-III, B-II, C-I, and D-IV. Hence, the answer is 3.