Researcher: Overhearing only one side of a cell-phone conversation diverts listeners' attention from whatever they are doing.
Statements
causal (diverts / leaves / because)
Overhearing one-side Diverts your of a cell-phone ⇢ attention from conversation what you're doing
Hearing only one ⇢ Constantly trying portion of conversation to guess what other person said
Hearing someone → diverts your speak abnormally loudly attention away
Evaluate
We have three related causal statements. They don't really link up to a causal chain, but they all stem from a related cause.
You're hearing your friend / loved one talking (abnormally loudly) on the cell-phone. You can only hear their part of the conversation. You're trying to guess what the other person just said or is saying.
And what does all that cause? It diverts your attention.
Goal
It's hard to know exactly what the answer will say, but it will seemingly reinforce this causal relationship being stressed that, for multiple reasons, eavesdropping on your friend's cell-phone cause is diverting your attention from whatever you are doing.