如下图示的积分电路，R=10kΩ，C=10μF，在t＜0时，U0=0V，t=0时，介入U1=1V的直流电压，求U0从0V下降到－5V

Vitamins are complex ________ that the body requires in very small mounts.

A．matters

B．materials

C．particles

D．substances

A、In general, excesses of fat-soluble vitamins cannot be excreted as easily as water-soluble vitamins.

B、In general, water-soluble vitamins are more likely to be stored in the body than fat-soluble vitamins.

C、The body has higher requirements for water-soluble vitamins.

D、The body has higher requirements for fat-soluble vitamins.

The body needs____for life and health.

A．extra vitamins

B．a good variety of vitamins

C．large amounts of certain vitamins

D．small amounts of each vitamin

The body needs______for life and health.

A．extra vitamins

B．a good variety of vitamins

C．large amounts of certain vitamins

D．small amounts of each vitamin

If you take in more vitamins than you actually need,_____.

A．they are harmful to your body

B．you get all the vitamins now known to be needed

C．they help our bodies more properly

D．your body simply gets rid of them

A．variety

B．fraction

C．section

D．series

How can a urine test show a patient may have a vitamin deficiency？

A．A lot of vitamins are in the urine.

B．The body refuses to absorb vitamins.

C．Only a few vitamins passes through the body.

D．A lot of vitamins are taken in by the body.

A．Y

B．N

C．NG

A．substances

B．materials

C．particles

D．matters