Bug: Typing '4' does not highlight 'lo' in single-word English->Italian translation exercises

[thenoblesunfish]

Typing '4' does not select the article 'lo' in the single-word English-to-Italian translation exercises, for a singular noun (whereas typing '1'-'3' does highlight the first three article options).

I have consistently observed this using Chrome and Safari within OSX 10.8 and 10.9.

[kay-mika]

It doesn't work in firefox, too

[thenoblesunfish]

This problem persists.