Pitch is produced by frequency of vibration of the vocal cords. The higher the freque

__________ is the variation of pitch to distinguish utterance meaning.

A、Stress

B、Pitch

C、Tone

D、Intonation

r the construction of what we call modern civilization. Every dispensable item of contemporary technology, from canal locks to dial telephones to penicillin, was pieced together from the analysis of data provided by one or another series of scientific experiments. Three hundred years seems a long time for testing a new approach to human interaction, long enough to settle back for critical appraisal of the scientific method, maybe even long enough to vote on whether to go on with it or not. There is an argument.

Voices have been raised in protest since the beginning, rising in pitch and violence in the nineteenth century during the early stages of the industrial revolution, summoning urgent crowds into the streets any day on the issue of nuclear energy. The principal discoveries in this century, all in all, are the glimpses of the depth of our ignorance about nature. Things that used to seem clear and rational, matters of absolute certainty—Newtonian mechanics, for example—have slipped through our fingers, and we are left with a new set of gigantic puzzles, cosmic uncertainties, ambiguities; some of the laws of physics are amended every few years, some are canceled outright, some undergo revised versions of legislative intent as if they were acts of Congress.

Just thirty years ago we call it a biological revolution when the fantastic geometry of the DNA molecule was exposed to public view and the linear language of genetics was decoded. For a while, things seemed simple and clear, the cell was a neat little machine, a mechanical device ready for taking to pieces and reassembling, like a tiny watch. But just in the last few years it has become almost unbelievably complex, filled with strange parts whose functions are beyond today's imagining.

It is not just that there is more to do; there is everything to do. What lies ahead, or what can lie ahead if the efforts in basic research are continued, is much more than the conquest of human disease or the improvement of agricultural technology or the cultivation of nutrients in the sea. As we learn more about fundamental processes of living things in general we will learn more about ourselves.

What CAN'T be inferred from the 1st paragraph？

A．Scientific experiments in the past three hundred years have produced many valuable items.

B．For three hundred years there have been people holding hostile attitude toward science.

C．For centuries scientific discoveries have been hailed by the human world unanimously.

D．Three hundred years is not long enough to settle back for critical appraisal of the scientific method.

The most powerful signal of stress is a change of pitch on the vowel.()

Intonation is the variation of pitch distinguishing utterance meaning. ()

Propeller pitch speed minus ship speed divided by the propeller pitch speed is termed

A.apparent slip

B.true slip

C.pitch

D.propulsive efficiency

A.long

B.away

C.far

D.often

A、Pitch oscillations becoming progressively greater

B、 Bank oscillations becoming progressively greater

C、Aircraft constantly tries to pitch down

Compared to a constant pitch propeller, a controllable pitch propeller

A.more efficiently uses available engine power

B.operates at a lower efficiency at a fixed speed

C.produces the same torque at lower engine power

D.develops its rated power at a lower speed