The opening of right atrium into right ventricle is guarded by alzy mitral valve .a tricuspid valve .b aortic semilunar valve .c bicuspid valve .d

The correct answer is option b: tricuspid valve.<br /><br />The opening of the right atrium into the right ventricle is guarded by the tricuspid valve. The tricuspid valve is a valve located between the right atrium and the right ventricle of the heart. It prevents the backflow of blood from the right ventricle into the right atrium when the right ventricle contracts.