Poll: Someone has left ..... books behind.

shaun

if u could see the 'books' the answer should be in singular form

khubib

males has priority in general discourse and vague situations in most languages.

aj

This is the 21st century. Leave out the gender

Teeter

SomeONE= singular... Their is plural

Stephan

'Their' is absolutely wrong. 'His' and 'her' are correct, but gender should be left out . 'His or her' is the most appropriate answer.

Jack

Since the sentence says Someone...you do not know their gender at all..ergo their