Imagine your body is like the house you live in．Every day, your family creates rubbish．The rubbish builds up until it is put out for the weekly garbage collection．
Now, say you put three bags of garbage out．but because one of the collectors was away sick, only two bags are collected．You take the leftover bag inside to be put out again next week．The following week you put on another three bags．plus the leftover bag from last week．But again, only two bags are collected．Imagine this cycle is repeated over the following weeks．
This is a simple description of what happens to your body when your kidneys （肾脏）don't work efficiently．Your body is nol thoroughly emptied of waste products．Other areas of the bodv such as blood pressure and red blood cell production are affected and the insidious process that may lead to kidney failure begins．
It's not uncommon for people to lose up to 90% of their kidney function before deveoping any symptoms．There may be no warning signs. This makes early detection （诊查）difficult．
Kidney's main job is to remote toxins（毒素） and unwanted water from our blood．Every day our kidneys clean an average of 200 litres of blood．Kidney failure may be a gradual and silent process, going unnoticed because there is no apparent pain．
Research shows that more than 35% of the patients requiring dialysis （透析）do not see a kidney specialist before they have to do so．Some risk factors for kidney disease such as age and genetic make up are out of our control; however, some changes in lifestyle may help prevent kidney damage．Two major risk factors for kidney disease, diabetes （糖尿病）and high blood pressure, have been on the rise over the last few decades．Both conditions are chiefly affected by being overweight and not getting enough exercises, which are the potential risk factors for the kidney disease．
66．The author gives the example of the house we live in to indicate that ______．
A．it doesn't matter much if the waste in our body is not emptied in time
B．our body will not produce any waste if our kidneys work efficiently
C．it's important for our body to empty the waste in time every day
D．it's safe and harmless for our body to keep some waste
67．The underlined word “insidious” in Paragrap 3 means          .
A．smooth and safe                 B．apparent and fast
C．gradual and unnoticed       D．long and painful
68．We can infer that when we find some symptoms related to our kidneys,          .
A．the kidney failure begins
B．the kidneys can still work properly
C．we have lost about 10% of kidney function
D．the kidneys may have been seriously damaged
69．How many risk factors of kidney disease are mentioned in the passage?
A．Six.     B．Five.  C．Four.  D．Two.
70．Which of the following helps prevent kidney damage most effectively?
A．Go to see a kidney specialist shortly before dialysis starts.
B．Take enough exercise and make early detection of kidney disease.
C．Try to keep low blood pressure and a stable lifestyle.
D．Go to hospital whenever you find any warning signs.