Reading and writing fill in the blanks practice exercise. Below is text with blanks. Choose the correct word for each blank to complete the text.

Life on Earth (1) …………………………. six basic ingredients—carbon, hydrogen, nitrogen, oxygen, sulfur and (2) ……………………….. Those six elements are the building blocks for DNA and RNA, along with proteins and fats. That means they’re very essential for life as we know it. Also, it might be time to update that list. Because (3) ………………………. have found a bacterium which can do even without phosphorus live on arsenic instead. And the researchers had a hunch a bug like this might exist, because arsenic has some chemical properties in common with phosphorus. So they (4) ……………………….. mud from California’s Mono Lake, where the waters are naturally salty, and laced with arsenic. Back in the lab, they cultured the microbes from that mud. But instead of adding phosphorus to the (5) …………………… to help the bugs grow, they added varying levels of arsenic. One bacterial strain continued to thrive. And tests confirmed that the organisms (6) ……………………………. for the lack of phosphorus by forming their DNA with arsenic instead. Research appears in the journal Science. This is the first known life form that seems to be able to swap out one of life’s (7) ………………………… building blocks with another element. Therefore, for astrobiologists hunting for life in space, don’t rule out places filled with poison.

(1) stipends, breathalyzers, requires, imbibers
(2) applets, phosphorus, tolerance, noncancerous
(3) scientists, licenses, likenesses, wirelesses
(4) singled, interdependent, envisioned, collected
(5) colors, cultures, infrastructures, youngsters
(6) favored, consolidated, vacationed, compensated
(7) drivel, fundamental, spindle, pebble

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