When it ______ research into heart disease and its effects on the body, we do not have adequate substitutes for the use of animals.
| A．refers to | B．related to | C．comes to | D．talks to |
— Do you play football after work? — Yes, _____. Playing football is not my favorite sport.
| A．more or less |
| B．once in a while |
| C．sooner or later |
| D．time and time again |
Jack took part in the speech contest and, ______ is more surprising, won the first place.
| A．that | B．what | C．which | D．it |
Living off home is a sure way to improve your self-care ability, and this is especially true ______ it comes to studying abroad.
| A．before | B．since | C．when | D．unless |
You should feel content, as the design can’t be done any ______.
| A．best | B．worst | C．better | D．worse |
_____ to nuclear radiation, even for a short time, may produce variants (变异体) of genes in bodies.
| A．Being exposed |
| B．Having exposed |
| C．Exposed |
| D．After being exposed |