Correct option is A
For grade 4.6 bolts:
Yield Strength: 240 N/mm²
Ultimate Strength: 400 N/mm²
The grade "4.6" denotes that the minimum yield strength is 4 x 10 MPa = 400 MPa (or 400 N/mm²), and the minimum ultimate tensile strength is 6 x 10 MPa = 600 MPa (or 600 N/mm²). However, in many specifications, the yield and ultimate strengths used are 240 N/mm² and 400 N/mm² respectively for practical applications.
Therefore, the correct answer is (a) 240 N/mm² and 400 N/mm².
