The structure that prevents food from entering the trachea is the: MCQ with Answer and Explanation

Explanation:
All three are correct: SA node initiates impulse, AV node delays it to allow atrial emptying, Purkinje fibers spread impulse through ventricles.

Explanation:
Phycology (algology) is the study of algae, which are photosynthetic eukaryotic organisms ranging from unicellular to multicellular forms. Mycology deals with fungi, bryology with mosses and liverworts, and pteridology with ferns. Algae include green algae, red algae, brown algae, and diatoms, and are important primary producers in aquatic ecosystems.

Explanation:
The double helix structure of DNA was proposed by James Watson and Francis Crick in 1953, based on X-ray diffraction data produced by Rosalind Franklin and Maurice Wilkins. They proposed that DNA consists of two antiparallel polynucleotide chains coiled around a common axis, with specific base pairing (A-T, G-C) holding the strands together.