Question

deficiency means :
lack of an adequate quantity or number
alert attentiveness
the property of two things happening at the same
time
intensity or forcefulness of expression

Explanation:

The word "deficiency" is related to the concept of lacking something. Among the given options, "lack of an adequate quantity or number" directly aligns with the meaning of deficiency. The other options: "alert attentiveness" is about being attentive, "the property of two things happening at the same time" is about simultaneity, and "intensity or forcefulness of expression" is about how strongly something is expressed, none of which match the meaning of deficiency.

Answer:

lack of an adequate quantity or number