Answer:
c. electron-pair donor.
Explanation:
Lewis base -
A Lewis base is an electron rich species , which is available for donation .
Hence , Lewis base is a electron - pair donor .
The indication of a Lewis base , is it has a negative charge or lone pairs of electrons .
Hence , the species with a lone pair or negative charge act as a Lewis base .
for example , OH ⁻ is a Lewis base , due to its negative charge which is available for donation .
H₂O is also a Lewis base , due to its lone pairs of electrons , that are available for donation .
