How many elements have currently been discovered

115

Explanation:

Elements 1 to 112, Hydrogen to Ununbium are known, with Ununbium only been discovered in 1996. Elements 114, 116 and 118 have also been discovered more recently, bringing the total to 115 known elements. Note that Elements 113,115 and 117 have not yet been discovered

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]