What receives radio waves from space objects such as quasars?
a. gps equipment
b. landsat satellites
c. vlbi equipment
d. navigation satellites

A VLBI system detects radio waves from space objects such as quasars.

"VLBI" stands for "Very Long Baseline Interferometry".  The idea
is that the signal is picked up by two receivers, separated by some
distance.  The tiny difference in the time the signal shows up at the
two places is used for a very precise calculation of the direction it's
coming from.

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the best answer for these questions would be:

1.            c. is smaller

2.            d) concrete operational

3.            b) interaction with the environment – the children interact with their environment can them learn more.

4.            a) parents who reason openly with children can limit a child’s cognitive ability.