[Answer] 9. At number 10, which mineral was long believed to be the hardest on Earth?

Step 1 : Introduction to the question "9. At number 10, which mineral was long believed to be the hardest on Earth?"

...1. Rubidite 2. Corundum 3. Diamond 4. Laitile Diamond is frequently quoted as the hardest mineral found, but later discoveries have rendered this incorrect - although diamond is still the hardest relatively common mineral and remains the hardest on the Mohs scale.

[Ans] Who said, "The hardest years in life are those between ten and seventy."?

Step 1 : Introduction to the question "Who said, "The hardest years in life are those between ten and seventy."?"

Helen Hayes died at the age of 92 in 1993. Her long career included stage, film and television and spanned over eighty years. She began her career as a child actress during the first decade of the 20th century. By 1920, she was already established as one of the greatest female stars of the theatre. She won two Oscars during her long career. Although she retired from the stage in 1971 but remained tremendously popular in television and motion pictures. She finally retired from acting in 1985. Her fame continued until her death in Nyack, New York, from congestive heart failure. Source: IMDb.com

[Answer] Which bone in the human body is the hardest?

Step 1 : Introduction to the question "Which bone in the human body is the hardest?"

...The mandible, or jawbone, is the hardest bone in the human body. It is also the strongest and largest of the bones in the face. The jawbone holds the lower teeth in place and connects to the skull behind the ears. The entirety of the jawbone forms while babies are in utero. First cartilage forms and then ossification takes place over several weeks to form the actual jawbone. During the first year of a child's life, the mandible hardens to become the strongest, hardest bone in the body. Source: Reference.com