【单选题】The types of short-circuit in three-phase system are three-phase short-circuit, two-phase short-circuit, two-phase short-circuit grounding and single-phase short-circuit grounding. When the three phases of the system are short-circuited, they are still in the symmetrical stated. Other types of shorted circuit are asymmetric short circuit. Which of the following types is a symmetrical short circuit? A. Single phsae ground short circuit B. Three phase short circuit C. Two phase short circuit D. Two phase ground short circuit

During<br/>cooling of a material, when a single phase solid transforms directly<br/>to two-phase solid, this is called a ( ) reaction. A: isomorphous B: eutectic C: peritectic D: eutectoid

A two-phase ac servomotor is also called a two-phase ______ motor.

Consider an interference between two waves. At a certain position if the vibrations caused by two waves are in phase, they make a destructive interference.? 正确|错误

The operation of _______two alternators requires the voltages to be equal and also in phase A.paralleling B.series-mounting C.running D.controlling

The first ______ of the project was completed two months ahead of schedule. A: process B: section C: span D: phase

Two light sources are said to be coherent if they ( ) A: are of the same frequency. B: are of the same frequency and amplitude. C: are of the same amplitude, and maintain a constant phase difference. D: are of the same frequency, and maintain a constant phase difference.

Which of the following is not a CT phase of COVID-19? A: Early phase B: General phase C: Progressive phase D: Critical phase E: Resolutive phase

Slug flow is the most efficient flow pattern in two-phase flow

The first phase of the stress response, or General Adaptation<br/>Syndrome is called the ( ). A: Resistance phase B: Adaptation phase C: Alarm phase D: Fight-or-flight phase