facultative

adj.

特许的；兼性的；

1. The last questions in the examination were facultative.
   最後的那些考题答兴不答可听自便。

Facultative bacterial symbionts in aphids confer resistance to parasitic wasps
Facultative symbionts in aphids and the horizontal transfer of ecologically important traits.
Host Plant Specialization Governed by Facultative Symbiont
Dark septate endophytes: a review of facultative biotrophic root-colonizing fungi.
Alcaligenes eutrophus CH34 is a facultative chemolithotroph with plasmid-bound resistance to heavy metals.
Escalated aggressive behaviour and facultative parental care in the nest building gladiator frog, Hyla faber
In vitro susceptibilities of aerobic and facultative Gram-negative bacilli isolated from patients with intra-abdominal infections wo...
In vitro susceptibilities of aerobic and facultative Gram-negative bacilli isolated from patients with intra-abdominal infections in...
Host-based divergence in populations of the pea aphid: insights from nuclear markers and the prevalence of facultative symbionts.
Ecological Aspects of Amphibian Metamorphosis: Nonnormal distributions of competitive ability reflect selection for facultative meta...