If ‘+’ sign is assigned to beneficial interaction, ‘–’ sign to detrimental and ‘O’ sign to neutral interaction

Question

If ‘+’ sign is assigned to beneficial interaction, ‘–’ sign to detrimental and ‘O’ sign to neutral interaction, then the population interaction represented by ‘+’ ‘–’ refers to

(a) mutualism

(b) amensalism

(c) commensalism

(d) parasitism.