In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. Your answer should be chosen from the given text, and should not contain other words.

Isambard Sinclair, narrator:  Is this the beginning of the end for Danger Mouse or only the end of the beginning ? Or is it three quarters plus a little tiny bit of somewhere around the middle ? Write your answers on a sliced loaf and tune in two the next enthralling installment of ' Four Heads Are Better than _ Two _ ' with Danger Mouse .
Heads

Boyd Langton:  The one who wanted to be rolled in eggs and flour and dipped .
Adelle DeWitt: Ahh , Tempura Joe . Such a lonely soul .
Boyd Langton: Thought I 'd seen it all . But this engagement , * honestly * , this _ one _ 's sick !
engagement

Penelope Garcia:  I have gone through every frequency and wavelength and , and I haven't been able to pick up on anything !
Kevin Lynch: Well , just slow down .
Penelope Garcia: I 'm frustrated
Kevin Lynch: I get that . Let 's just go back . You 've checked audix ?
Kevin Lynch: Yes
Kevin Lynch: All right , Nady systems , AKG , Electro - Voice , VocoPro ?
Penelope Garcia: Yes , yes and yes . Gone through all every frequencies in the freaking northern hemisphere , and nothing !
Kevin Lynch: I do n't know , I mean these are the only frequencies that are above ground
Penelope Garcia: Wait ! Underground !
Kevin Lynch: No , I said : above ground
Penelope Garcia: ELF ! Extremely Low Frequency . It 's the only _ one _ that can penetrate underground Got a hit You 've lipstick on your face

ELF