1000sc

[chimni]

1. Biologists believe that they have found one of the substances that tell individual genes both when to become active and when to remain quiescent in the earliest phases of an embryo’s development.

(A) tell individual genes both when to become active and when to remain

(B) tell individual genes both at which time they should become active or should remain

(C) tells individual genes both when to become active or remain

(D) tells individual genes both when to become active or when to remain

(E) will tell an individual gene both about when it should become active and remain

Could somene explain tense here. (relatively easy but confused me)
One of the substances is talking about one thing so should be singular.
On the other hand substances is plural

one of the boy's has come (singular)

[karmaholic]

Its D. Reason being that the "object" here is "substances" and is singular here, further is receives the verb "tells".
The difference between "when to become active or remain" and "when to become active and when to remain" is that the later is idiomatically correct. I need to brush up my grammar.

[chimni]

The Official Answer is A

[800Bob]

"One of the (plural noun)" is followed by a singular verb. Example:
One of the restaurants was open.

"One of the (plural noun) that" is followed by a plural verb. Example:
We ate at one of the restaurants that were open.

This is no arbitrary rule. It's logical. In the first example, there was only one restaurant that was open. In the second example, there were a plural number of restaurants that were open.

In the example under discussion, the substance found by biologists is just one of a plural number of substances that have the given characteristic.

[chimni]

800bob thanks.
Could'nt help noticing the milan .Currently in Italy .Hope the weather improves my IQ