Riding Level Four

I can't figure out this question... Can you help?

The quality of soil on which the horse works is very important, check the right statements:

• The frog has a shack-absorbing role; it must be released to work well
  
• Deep soil tires out the tendons
  
• Sticky soil which forms packets under the horses hooves enable it to absorb shocks better
  
• Mixed soil is harmul to horses as it tires out both tendons and joints
  
• Hard soil tires out the joints