If “+” sign is assigned to beneficial interaction, “-” sign to detrimental and “0” sign to neutral interaction, then how many of the following is/are representing “+” and “-” interaction in a broad ecological context?
a) Orchid growing on a mango branch
b) Sea anemone and clown fish
c) Lichens
d) Sparrow eating any seed
e) Cuscuta on hedge plants
f) Marine fish infested with ectoparasitic copepods