A.when the moon is new or full
B.when the moon and sun have declination of the same name
C.only when the moon and sun are on the same sides of the earth
D.at the beginning of spring when the sun is over the equator

A.at the start of spring，when the Sun is nearly over the equator
B.only when the Sun and Moon are on the same side of the Earth and nearly in line
C.when the Sun and Moon are at approximately 90°to each other as seen from the Earth
D.when the Sun，Moon，and Earth are nearly in line，in any order

A.have lows lower than normal and highs higher than normal
B.have lows higher than normal and highs lower than normal
C.are unpredictable
D.occur in the spring of the year

A.its velocity in knots
B.direction from which it flows
C.estimated current
D.direction toward which it flows

A.interruption of the normal current flow by the footing
B.elevating in mud-slide zones
C.penetrating rapidly through a hard crust into weaker soils
D.extracting legs from soils with high cohesion