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How does helicobacter pylori cause stomach ulcers?

It neutralises acid in the stomach and allows bacteria to damage the stomach epithelium.

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If a race car completed a full lap and is where he started, why is his average velocity zero but his average speed isn’t?

Velocity is displacement over time, whereas speed is distance over time. Displacement is the shortest distance from point A to point B(a straight line). In this case, the starting point(point A) is the en...

Answered by Osman O. • Physics tutor

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Where and why do we plot points on cumulative frequency graphs?

At the end of each group. Say you have a table of groups and frequencies corresponding to those groups, for example for x we have group 0<x<=5 with frequency 6 and group 5<x<=15 with frequency...

Answered by Osman O. • Maths tutor

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How do I know which ending to use after the preposition «в»?

The preposition «в» has two meanings: in/on or to (as in movement, going to a place). When it means in or on, the noun which follows must be in the prepositional case, ending in «е». For example «мальчик ...

Answered by Eleanor B. • Russian tutor

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Before a drug is sold and released to the public, what measures must scientists take to ensure the safety of a drug and why are these steps taken?

Phase I- The drug must be tested on animals and tissue culturesPhase II - The drug is tested on healthy volunteers in small dosesPhases III- The drug is tested on sick patients in small dosesSmall doses a...

Answered by Saranya G. • Biology tutor

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