這是一篇短文，講到有些人天生有「共感(synesthesia)」，
例如聽覺併味覺（聽到聲音的時候，覺得聲音有味道）、不同字母有不同的顏色。
目前科學家初步認為這是基因的關係。
"Currently, synesthesia is not completely understood, but it is believed to
be in our genes. Scientists find that the white matter of synesthetes is
organized differently from that of people without synesthesia. This may
account for the differences in perception. Nontheless, some scientists think
all people _____________ with synesthesia only to lose it later on in their
lives."
(A)were born (B)may be born
(C)may have been born (D)may not have been born
空格處答案是C。請問為什麼？A、B、C有什麼不同？謝謝！