Reading — Viruses and Bacteria

"The two most common causative agents of infectious diseases are the virus and the bacterium."

ما معنى causative agents؟ وما الصورة العلمية التي يستخدمها الكاتب؟

"They both are tiny to be seen by the naked eye, they can cause similar symptoms and are often spread in the same way."

ما وظيفة to be seen في هذه الجملة؟ وكيف يختلف عن for seeing؟

"Bacteria are living organisms, but viruses aren't."

ما وظيفة aren't في نهاية هذه الجملة؟ وماذا تسمى هذه الصيغة؟

"A bacterium is a single complex cell. It can survive on its own, inside or outside the body."

ما الفرق بين bacterium وbacteria؟ وما نوع هذا الجمع؟

"They also serve many vital roles in nature by decomposing organic matter and by converting nitrogen to chemicals usable by plants."

لماذا تكررت by مرتين في هذه الجملة؟ وما وظيفتها النحوية؟

"Unlike bacteria, they need a host such as a human or an animal to multiply."

ما وظيفة Unlike في بداية الجملة؟ وما الفكرة التي يبنيها الكاتب؟

"Their life involves the hijacking of the biochemical activities of a living cell."

ما معنى hijacking في هذا السياق؟ وما الصورة البلاغية فيه؟

"It can be very difficult to know what causes an infection because viral and bacterial infections can cause similar symptoms."

لماذا استخدم الكاتب can be وليس is في بداية الجملة؟