Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: Washington (CNN) Sen. Marco Rubio, a longtime hawk on Syria, praised the US airstrike on a Syrian airfield days after a chemical attack on innocents attributed to Syrian President Bashar al-Assad. Following news that President Donald Trump had green-lit the US action, Rubio said Thursday on CNN's "Anderson Cooper 360" that Russia could not fairly criticize the military strike because Russia backed Assad -- who is accused of perpetrating the attack on his own people. "They have no standing to say anything about this," Rubio said of the Russians. He said that the move doesn't just send a message, but amounts to a "significant degrading" of Assad's ability to carry out chemical attacks.Rubio said Russians had put themselves into harm's wayHe said the strikes indicated a firm US stance against Assad's reign 
 Question:"If the Russians are there on the ground assisting _ in the commission of these heinous crimes -- war crimes -- they should answer for that," Rubio said.

Assad