Read the text and determine if the sentence is true (see options at the end):

In this Wednesday, Aug. 16, 2017 photo, a nurse attends to Argelia Mansio who was injured by a stray bullet during an assault staged by unknown attackers at the Roosevelt Hospital, in Guatemala City. The deputy hospital director told reporters that 12 people were wounded, including a child who underwent surgery and was in critical condition. Luis Soto AP Photo

Sentence: The attackers were unknown.
Choices:
 A). Yes;
 B). It's impossible to say;
 C). No;