Here is your paragraph written normally, with all the articles in italics.
<em>The</em> highest mountain in Great Britain is <em>the</em> Ben Nevis, which is situated in <em>the</em> Grampians (a mountain range).
<em>The</em> Pennines are <em>the</em> mountains situated in <em>the</em> central part of Great Britain. They are separated from <em>the</em> Southern Uplands by <em>the</em> valley of River Tyne. <em>The</em> Tyne flows into <em>the</em> North Sea.
<em>The</em> mountain range called <em>the</em> Cambrians is in Wales. <em>The</em> highest mountain in <em>the</em> Cambrians is <em>the</em> Snowdon.
<em>The</em> longest river in Great Britain is <em>the</em> Severn. It rises in <em>the</em> Cambrians and flows into <em>the</em> Bristol Channel. <em>The</em> River Thames is not as long as the Severn but it is <em>the</em> most important river in Great Britain. London, <em>the</em> capital of the United Kingdom, is situated on <em>the</em> Thames.
Next time, please use an image to text generator and paste that into your lesson, so your answerer doesn't have to do that or retype it or anything.