Read the excerpt from the dark game.

the first thing about the zimmermann telegram that two room 40 code breakers, reverend william montgomery and nigel de grey, noticed was its length, more than a thousand groups. although the length itself was not suspicious, it was out of the ordinary. then de grey noticed the top group of numbers in the message, 13042, a variation of 13040, indicated a german diplomatic code. since room 40 had a copy of the 13040 codebook, they began using it to decipher the message.

which details in the text indicate a chronological structure? check all that apply.

the first thing
although
then
since