Steroid is contraindicated in –
Herpes keratitis
Atropic dermatitis
Fungal corneal ulcer
Exposure keratitis
here: -Topical corticosteroids enhance fungal replication and corneal invasion and therefore, contraindicated in a fungal corneal ulcer.
Now, option 'a' requires specific mention here:-
Topical corticosteroids are contraindicated in herpetic keratitis. But not in all forms of herpetic keratitis :-


Epithelial herpetic keratitis (Dendritic ulcer, geographic ulcer) → Topicla corticosteroids are contraindicated.
Stromal keratitis (Disciform & Diffuse necrotic) → Topical corticosteroids along with topical antiviral drugs are used as the first line of treatment.


So, my opinion for this type of question is that :-

i) If herpetic keratitis has given as the option, then look at other options. If any of the other options is a clear cut contraindication for corticosteroid (e.g. fungal corneal ulcer in this question), consider that option as your answer. If no ther option is a contraindication for topical corticosteroid, consider herpetic keratitis as the answer.
ii) If examiner has specifically mentioned dendritic ulcer as an option, consider it as the answer.